Documentation

Supported formats

Worked reports from real exports: Interactive Brokers · Trading 212 · multi-broker.

Supported Brokers

Generic CSV Format

Create a comma-separated .csv file or start with the canonical template. Headers are case-insensitive and may appear in any order; extra columns are ignored. Numbers may group thousands with commas (1,121.76); a decimal comma (103,86) is refused rather than guessed.

Example file

Supported actions

Action names are case-insensitive. Keep the header row in the file.

Required headers: Date, Action, and at least one of Symbol, Ticker, or ISIN. A buy or sell also needs a positive Quantity and Price. Sell quantities may be written as positive or negative; they are normalised to a disposal.

Dates: use YYYY-MM-DD, YYYY/MM/DD, UK DD/MM/YYYY, or US MM/DD/YYYY; a two-digit year such as 28/01/25 also works. The order is decided for the whole file: one date like 28/01/2025 makes every date in it day-first. If no date settles it, 01/02/2024 means 2 January. Invalid calendar dates are excluded with a row warning.

Spouse transfers: SPOUSE_TRANSFER_OUT removes the quantity and its Section 104 cost without a gain, loss, proceeds, or reportable disposal. SPOUSE_TRANSFER_IN adds shares on the transfer date using the required total Transferred_Allowable_Cost_GBP; Price is ignored for both actions.

Downloadable cookbook:

• Basic Generic CSV and GBP trades
• GBX shares with GBP fees
• One foreign currency and different share and fee currencies
• User-supplied rates and automatic historical rates
• Spouse transfer in/out and mixed portfolio

cgtcalculator.com Format

In cgtcalculator.com, select Format/Sort, copy the Trades field, and save it as a .txt file.

Example file

Column labels are not part of the file.

Supported commands

Separate fields with spaces or tabs; do not add a header row. Trailing U/L markers are accepted but ignored because they belong to discontinued taper relief rules. Trades before 6 Apr 2008 produce a warning.

Interactive Brokers (IBKR)

The most complete integration — stocks, options, corporate actions, FX trades, dividends and interest. Use the Activity Statement CSV; the simple trades export leaves out options. More on the Interactive Brokers CGT calculator page.

Trading 212

Stocks, ETFs, dividends, interest and stock splits (2020 and 2024 export formats). Invest/ISA only — CFD accounts aren’t supported. More on the Trading 212 CGT calculator page.

Trading 212 exports by calendar year, so a full UK tax year (6 Apr – 5 Apr) needs two exports.

Charles Schwab

Stock trades, options, dividends, interest, RSUs and cash mergers. If you have equity awards (RSUs), upload both the Brokerage CSV and the Equity Awards CSV together so vest events get their cost basis — adding the awards file later on the edit page won’t link them. More on the Charles Schwab CGT calculator page.

US Treasury bills held to maturity are treated as Deeply Discounted Securities: the discount is booked as foreign interest, not a capital gain. Detected automatically — no manual flagging needed.

Freetrade

Stock trades, dividends (with withholding tax), gilts with their coupons, cash interest and share-lending income. Stamp duty and FX fees are read automatically. Corporate actions aren’t included — contact Freetrade support for a full statement. More on the Freetrade CGT calculator page.

Stock, fund and ETF trades plus credit interest, from the Transaction summary CSV in the Tax centre — the Portfolio history download has the same columns and works too. Everything is in sterling, so no FX is involved. The dealing charge isn’t stated in the file; it is read back from the gap between the trade and the cash amount. More on the Hargreaves Lansdown CGT calculator page.

HL rows carry no ISIN and no ticker, so holdings are matched by name: rename a fund between two exports and its pool splits in two. Give both halves the same name on the edit page and they pool again — an ISIN won’t do it, because pools are keyed on the name.

Gilts are recognised from their name. A row such as Treasury 0.125% 31/01/2028 Gilt is matched against the UK Debt Management Office register on its coupon and redemption date, so the disposal is exempt even though the export states no ISIN. A gilt fund is not — the exemption covers gilts themselves, not units in a fund that holds them.

Morgan Stanley (MSSB)

For RSU/equity-award holders. You need two files: the Releases Report (vest events) and the Withdrawals Report (sales and transfers). Without the Releases Report you’ll see “no purchase record found”, because vests are stored separately. The Releases Net Shares Report works as a vest source too, and UK-locale exports with £ prices are read as sterling directly — uploading both release reports together won’t double-count. More on the Morgan Stanley CGT calculator page.

Revolut

Stock trades, dividends (with withholding tax) and stock splits. Upload the Account Statement (Excel or CSV) — the “Income from Sells” profit/loss summary is not a valid input. More on the Revolut CGT calculator page.

Crypto has its own account statement, recognised on sight. Buys and sells (including Revolut X) in £, € or $ are converted at HMRC monthly rates, fee included in cost. Staking and Learn rewards are miscellaneous income at the day’s value and join the pool at that cost. Stake/Unstake and Send/Receive to your own wallet are not disposals (CRYPTO22100): coins move at cost, the withdrawal fee is not allowable. See Crypto for details.

Stock trades, options, dividends, cash-sweep interest, FX conversions and UK stock rewards from the Robinhood UK account activity report. Written options follow HMRC CG55545, including buy-to-close and assignment adjustments. USD amounts use HMRC monthly average rates — worked through on a sample statement. More on the Robinhood UK CGT calculator page.

Two platforms share the name. Both are supported, and whichever you upload is recognised on sight. More on the Fidelity CGT calculator page.

Fidelity.co.uk (Fidelity International) — fund and share trades (including the units Fidelity sells to settle its service fee), fund distributions, dividends, charge rebates, stock splits and cash interest from the Transaction history CSV exported with All Transactions. Dealing fees, stamp duty, the PTM levy and FX charges are matched to their trades automatically, and no FX conversion is needed. Upload both tax-year files when a holding spans years; a Custom export of the same account uploaded alongside is matched by reference number and not counted twice. ISA, Junior ISA and SIPP rows in All Accounts exports are skipped.

Fidelity.com (US) — stock trades and dividends from the History CSV. Trades are in USD, converted at HMRC monthly average rates; dividend reinvestments into the core cash fund (e.g. SPAXX) are treated as purchases — worked through on a sample export.

Fund and ETF trades, dividends and cash interest from the Vanguard Investor UK Client Transaction Listing. Everything settles in sterling, so no FX conversion is involved. ETF dealing fees are treated as an allowable incidental cost of the trade (TCGA92/S38); the platform Account Fee is not allowable for CGT, so it is excluded. More on the Vanguard CGT calculator page.

Upload the .xlsx as it downloads — every sheet is read, so there is no tab to pick. The General Account tab produces the report; ISA, Junior ISA, SIPP and Summary tabs are skipped, and you are told which. The workbook is checked against itself too: Vanguard’s running Balance column has to tie out to the penny, and where it doesn’t we refuse the file by name rather than report a number we can’t stand behind.

Stock and gilt trades, dividends, gilt coupons and cash interest from the ii Transaction history CSV — a debit/credit cash ledger, one per currency. More on the Interactive Investor CGT calculator page.

Gilts are recognised from their SEDOL. The export carries no ISIN, so one is derived from the SEDOL and matched against the UK Debt Management Office register: gilt disposals come out CGT-exempt (TCGA92 s115), and a gilt coupon — which ii labels Div in the ledger — is booked as savings interest, not a dividend, because that is what it is for the SA100.

Foreign-currency purchases (e.g. buying US dollars ahead of a trade) are recorded as FX acquisitions, so a later conversion back to sterling is matched against the pounds you actually paid.

Currency sub-accounts have their own ledger. Shares bought in Canadian or US dollars sit in a separate Transaction history whose figures all read CA$ or US$; upload it together with the sterling ledger. Those trades are booked in their currency and converted at the HMRC monthly rate, and a conversion that appears in both ledgers under the same Reference is counted once.

US dividends on the dollar ledger arrive net of withholding. ii credits what is left after the 15% US treaty tax and never shows the tax. For a company named like a US corporation (INC, CORP), the calculator rebuilds the gross and books the tax for Foreign Tax Credit Relief on SA106: $48.96 on 60 shares is 60 × $0.96 = $57.60, with $8.64 withheld. Dividends from other companies are booked as paid. Check either against the dividend voucher and correct it on the edit page.

Fund, share and ETF trades plus cash interest from the AJ Bell Transaction history CSV. Everything is in sterling, so there is no FX to convert. Export the Dealing account only — the file doesn’t say which account it came from, and ISA, Lifetime ISA and SIPP gains are tax-free. More on the AJ Bell CGT calculator page.

Add the Cash statement too

It carries income the Transaction history does not: cash interest, gilt coupons (savings interest, not dividends) and fund charge rebates. A rebate is other taxable income with basic-rate tax already taken off, so it goes in boxes 17 and 19 of your main return. Its purchases and sales are left to the Transaction history, so uploading both never counts a trade twice.

Charges

The file has no fee column, so charges are worked out for you (allowable under TCGA92/S38):

On a fund priced at hundreds of pounds a unit, AJ Bell rounds the unit count so much that the charge can’t be separated from the rounding. That row shows no charge rather than a guess; the gain is unaffected.

Holdings are pooled by name

The file has no ticker, ISIN or SEDOL, so the fund name identifies a holding. If the same fund appears under two spellings, or you also hold it at another broker, give both the same name on the edit page and they pool as one.

Binance

Cryptocurrency trades from two exports: Trade History (spot buys/sells — covers most people) or Statements (also includes staking rewards, airdrops and BNB dust). Upload both if unsure — duplicates are removed automatically. See Crypto for how swaps, fees and rewards are handled, and the Binance CGT calculator page for the worked example.

Coinbase

The Coinbase Retail transaction-history CSV that any Coinbase.com user can export. Covers Buy/Sell, Advanced Trade, Convert (crypto-to-crypto swaps), Receive, Send and staking rewards. See Crypto for how swaps, fees and rewards are handled, and the Coinbase CGT calculator page for the worked example.

Multi-Broker Support

Manual Transaction Entry

No usable export? Add trades by hand — date, ticker, action, quantity, price, fees and currency, in any currency the Broker tab offers. A non-sterling row is converted at the HMRC monthly rate unless you type your own FX/GBP rate, the same way the generic template’s Share_FX_Rate_To_GBP works. They sit alongside imported rows and follow the same HMRC matching rules, so this also covers a one-off correction or a trade your export is missing.

Report Output

Understanding your CGT report — what each section means and how to use it for Self Assessment.

What’s in Your Report

The report is organised into sections. Not all sections appear every time — you only see the ones relevant to your data.

Self Assessment (SA108)

The Self Assessment Summary at the top of your report gives you the numbers for HMRC’s SA108 Capital Gains page. SA108 splits disposals into separate sections by asset type — you enter the totals for each section into a different group of boxes:

Box numbers are taken from the SA108 form for 2025-26 (year ending 5 April 2026). The Cryptoassets section (boxes 13.1–13.8) was added from 2024-25 onwards — before that, crypto disposals went into “Other property, assets and gains”.

For UK dividends and UK interest, use the Income Summary to fill in the relevant boxes on your SA100 main return.

Self Assessment (SA106 — Foreign income)

Foreign dividends and overseas interest go on the SA106 Foreign pages, not the main return. SA106 is one line per country, so the report lays your foreign income out the same way:

Where the country comes from

• the jurisdiction named on your broker’s withholding row, if there is one;
• otherwise the holding’s ISIN — its country of registration, never its trading currency. A German company paying in euros is Germany, not Ireland.

Foreign Tax Credit Relief is the smaller of the foreign tax paid and the UK tax on that income, capped at the treaty rate (see Dividends & interest for the maths).

Rows you have to finish

Some exports do not carry enough to name the country. Rather than guess, the report gives the holding its own row and marks it:

The table helps you choose. Beside each holding it shows the rate actually withheld: where only one country withholds at that rate (Japan 15.315%, Taiwan 21%, Denmark 27%) the row is pre-filled for you to confirm; where several do (25% is Ireland, France, Canada and Norway alike) it lists them and you pick. Name a country the rate contradicts and the row is marked, and the next report carries a Dividend tax mismatch warning. Retyping a row’s ticker clears its country.

Tax withheld above the treaty rate

The excess is not creditable against UK tax — you reclaim it from the country that took it, not from HMRC. Novo Nordisk withholds Denmark’s 27%, so nearly half of it comes back from the Danish authorities. That is also why column C can read less than your broker deducted: HMRC defines it as the lower of the tax withheld and the credit the treaty allows (HS263). The report shows you the difference.

Small amounts

You can skip SA106 and use the SA100 instead: foreign dividends in box 6 up to the year’s limit (£500 from 2024/25, £1,000 for 2023/24, £2,000 before that, counting UK dividends too) and up to £2,000 of foreign interest in box 3. The report says so under the grid when your figures fit.

See it on a real report: the foreign dividends example. For a plain-English walkthrough, read Self Assessment for investors.

Downloading Your Report

The Download button on your report opens a short menu, grouped by file format. Under PDF, pick Full report for a print-ready view, then save it with Ctrl+P (Windows) or Cmd+P (Mac).

When your report has both capital gains and income, the same group offers just the part a Self Assessment section needs:

• Capital gains · SA108 — summary, the SA108 guide and every disposal section, for your capital-gains pages
• Income · SA100 / SA106 — the SA100/SA106 box guide plus your dividends, interest and ERI, for your income pages
• Full report — everything, including your Portfolio Holdings carry-forward snapshot

Foreign dividends and interest are income, so they appear only in the Income and Full reports — never in the capital-gains file.

All data (CSV)

Under CSV the same menu offers All data: one spreadsheet with everything the report has, for anyone who would rather work in Excel than read a PDF. It saves as cgtcalculator-<name>-<tax year>.csv, using the taxpayer’s name when you have set one (see below).

Layout

The first column of every row names its table — DISPOSAL, DIVIDEND, HOLDING, SA_BOX, and so on — and each table starts with its own header row. Filter on the first column to get one clean table at a time.

What no broker export has

• The exchange rate actually used on every transaction, and the trade converted at it — check it against the HMRC monthly rate by hand.
• The working behind each figure — the purchases matched against every disposal (shares, currencies and options alike), income tax by band, Foreign Tax Credit Relief per country.
• Your Advanced settings — residency periods, spin-off splits, interest and non-reporting fund tickers, ERI entries.

Reading the numbers

• Rounding — sterling totals are rounded to the penny; quantities, exchange rates and per-unit costs are written in full, so quantity × average cost still reconciles with the total beside it.
• Moved cost — a transaction’s sterling column is the broker’s own line converted. Where a rule moves cost between rows, such as an assigned option’s premium joining the shares it bought (CG12313), the figure the calculator used is in OPTION_ASSIGNMENT and HOLDING, not beside the trade.
• Leading apostrophe — a text cell that would start with =, +, - or @ gets one, so a description like - TW Tax stays text instead of becoming a formula. Delete it if you would rather not see it.

Re-importing the File

The same CSV is your report’s save file. Drop it on the upload page on its own and the report comes back as you left it — transactions, hand edits, Manual-tab rows, every Advanced setting, taxpayer details and the original broker statements, so Add files on the Edit page still works. Restoring a report you already paid for costs no report credit. The statements embedded in the file stay in your browser; only the transaction rows and settings are sent for recalculation.

• Figures are recalculated, not copied — an older export comes back under the current rules. If the total differs from the one in the file, the report opens with both figures side by side.
• Edited in a spreadsheet? The calculator trusts the transaction rows, not the totals, so the same notice appears. Re-save as CSV with the rows intact.
• Damaged file — refused, not guessed at.

Your Name and UTR on the PDF

Filing for more than one person? Put the taxpayer on the document so you can tell one computation from another.

In Edit → Tax Profile → Taxpayer details, fill in what you want, Save, then download. Name, UTR and Broker / account are each optional, and only the ones you set are printed:

• a band under the header: TAXPAYER John A. Smith UTR 1234567890 BROKER IBKR · U1234567
• the name at the end of the footer line, so a loose page still says whose it is
• the suggested filename: Tax Report - John A Smith - 2024-25 - Securities
• in the CSV: the file’s first row, and its filename

All three PDF downloads carry the band, and searching Recent by name finds the report. The values stay in your browser and are never sent to us — they are labels, so they cannot change a figure. See Privacy & Security.

Engine Version

Every report is stamped with the version of the calculation engine that produced it, shown as v1.27 at the bottom of the report. When a rule changes the version goes up, and your saved report is marked out of date so you can recalculate it against the current rules. The changelog lists what changed in each version — click the stamp on your own report to jump straight to its entry.

Share Matching Rules

How HMRC matches your sell transactions to your buy transactions to calculate capital gains.

When you sell shares, HMRC doesn't let you choose which purchase to match the sale against. Instead, three rules are applied in a strict order. You can't skip or reorder them.

1. Same Day Rule

If you buy and sell the same stock on the same calendar day, those transactions are matched against each other first, before any other rule. All acquisitions on that day are pooled and matched against all disposals on that day.

2. Bed & Breakfast Rule (30-Day Rule)

After same-day matching, any remaining sold shares are matched against purchases made within the next 30 calendar days. This anti-avoidance rule stops you from selling shares and rebuying them shortly after to create an artificial loss. The 30-day window runs forward from the sale date, not backward.

3. Section 104 Pool

Any shares not matched by the first two rules come from your Section 104 pool — a running total of all your purchases at their average cost per share:

Short Positions

If you sell shares you don’t own (short selling), the calculator tracks the short position separately. When you buy to cover, purchases are matched to the short sale in first-in-first-out (FIFO) order. Gain or loss is calculated as the difference between the sale proceeds and the covering purchase cost.

How Fees Are Handled

When you buy shares, any broker fees and commissions are added to your cost basis. When you sell, fees are deducted from your proceeds.

Option traders: if you're assigned shares from a short put, the Same Day and B&B rules still apply. Sell assigned shares and rebuy within 30 days? B&B kicks in.

Corporate Actions

How stock splits, mergers, spin-offs and ticker changes affect your cost basis.

When a corporate action occurs, the calculator adjusts your Section 104 pool automatically. Here is what is supported:

Stock Splits

When a company does a stock split (e.g. 4:1), your share count increases but your total cost basis stays the same. You just have more shares, each worth less. A reverse split (e.g. 1:10, common for leveraged ETFs) is the mirror image: your share count decreases and each remaining share carries proportionally more cost. Either way it is a reorganisation, not a disposal — no gain or loss arises, and the pool’s total cost is unchanged.

Note: Stock splits during a Bed & Breakfast 30-day window are handled automatically. The calculator adjusts matching quantities so pre-split disposals match correctly against post-split acquisitions.

Broker quirk (TD Ameritrade / Schwab): after a reverse split, TDA-migrated exports can report the same holding under a numeric CUSIP before the split and its plain ticker afterwards. The calculator recognises these as one security and applies the split from the migration journal, so your cost basis carries across instead of splitting into two holdings.

Cash Mergers

When a company is acquired for cash, all your shares are exchanged for cash at the merger price. The calculator treats this as a disposal — you receive proceeds and a capital gain or loss is calculated against your cost basis.

Spin-Offs

When a company spins off a division into a new public company, your cost basis is split between the parent and the new company. TCGA 1992 s126–131 sets the split by the two holdings’ market values on the first day they trade separately — a figure no broker statement carries, so it is the one corporate action you have to supply yourself. Take the percentage from the parent company’s investor relations page (US spin-offs usually publish it in the Form 8937), then enter the parent ticker, the new ticker and that percentage under Edit → Advanced → Spin-Off Cost Allocation.

Until you enter it, the spun-off shares stand at nil cost and the report carries a warning naming them. Selling them in that state is taxed on the full proceeds, and the parent’s pool keeps cost that should have moved across — so the gain is overstated now and understated later.

The percentage splits the cost of a spin-off your data reports — it cannot create the holding. If the statement you uploaded does not cover the distribution, the new shares never reach a pool, selling them reads as a disposal with no purchase on record, and the report says the allocation went unused. Upload the statement covering the spin-off, or add the row under Edit → Broker Transactions with the type Spin-Off, the new ticker, the shares received and the date.

Ticker Renames

When a company changes its ticker symbol, the calculator merges the old and new pools automatically. Your cost basis transfers to the new symbol with no tax event. The following renames are handled automatically:

An old ticker can be taken by another security later, so the rename is decided row by row. A row that carries the company’s ISIN is renamed whatever its date. A row without one is renamed only while the old ticker still belonged to that company: FB is read as META from Meta’s IPO on 18 May 2012 until 25 June 2025 — since 26 June 2025 FB is the ProShares S&P 500 Dynamic Buffer ETF and keeps its own pool. If your ISIN-less FB rows fall on both sides of that day, the report carries a warning; write META on the Meta rows to make it certain.

Return of Capital

Sometimes a company returns capital to shareholders. This isn't income — it reduces your cost basis instead. If you later sell the shares, your gain will be higher because your cost basis is lower.

Stock Dividends

When a company pays a dividend in shares instead of cash, the new shares are added to your Section 104 pool. Their cost basis is the market value on the dividend date. This is not a disposal — no capital gains tax is due at the time you receive the shares.

Transfers In & Out

When you transfer shares between brokers, no CGT event occurs:

• Transfer In — shares transferred from another broker are added to your Section 104 pool with their original cost basis.
• Transfer Out — shares transferred to another broker are removed from the pool. The receiving broker inherits the cost basis.

Options Trading

How call and put options are taxed under UK rules — from simple covered calls to complex multi-leg strategies.

HMRC has a special rule for options: when you write (sell) one, the date you write it is the CGT event — not when it later closes.

How Options Are Taxed

There are three ways an option position can end: you close it, it gets exercised/assigned, or it expires. Each has different tax treatment.

Writing (selling) an option — the premium you receive is treated as disposal proceeds. The date you wrote the option is the CGT date. Here is the simplest case — writing an option that expires worthless:

Buying an option — the premium you pay becomes your cost basis. Sell it later for a gain or loss.

Expiration — when an option expires worthless, the outcome depends on which side you were on:

Exercise and Assignment

When an option is exercised or assigned, HMRC doesn’t tax the option separately — the premium adjusts what you paid (or received) for the stock.

Exercise — you exercise your long option. The premium you paid gets added to the stock cost:

Assignment — your short option gets assigned. The premium you received reduces the stock cost:

Cross-Tax-Year Trades

If you write an option in one tax year and close it in the next, the calculator splits the tax correctly across both years. The premium is taxed in the year you wrote it, and the closing cost creates a repay entry in the closing year. Our blog follows this end to end for the wheel strategy.

Supported Strategies

The calculator processes each leg of a strategy independently. Here is what we test and support:

Crypto

How UK Capital Gains Tax applies to cryptocurrency, and how we handle your Binance, Coinbase and Revolut crypto data.

How HMRC Taxes Crypto

HMRC treats crypto as property, not currency (CRYPTO22200). Selling, swapping, or spending crypto is a disposal — and Capital Gains Tax applies. The gain or loss is the difference between your disposal proceeds in GBP and the cost from your Section 104 pool.

The matching rules are the same as for shares — see Share Matching.

Crypto-to-Crypto Swaps

Swapping one token for another (e.g. BTC for ETH) counts as two events under HMRC rules: a disposal of what you gave up and an acquisition of what you received. We split these automatically, which is why your report may show more lines than trades.

Fees are allocated to the first side only, to avoid double-counting.

Stablecoins

Stablecoins are pegged to fiat, so we map them to their fiat equivalent. A BTC/USDT trade is treated as BTC/USD — and the USD amount is then converted to GBP at the HMRC daily rate.

We recognise USDT, USDC, BUSD, DAI, TUSD, FDUSD, USDP, UST, USD1, USDS, USDSOLD, RLUSD, PAX, and VAI as USD equivalents. AEUR and EURI map to EUR, GYEN to JPY. Anything not on the list is treated as a crypto-to-crypto swap and priced independently.

Binance (Trade History + Statements), Coinbase Retail (all four header variants) and the Revolut crypto account statement are supported. See Supported formats for export instructions.

Fees

Exchange fees can be paid in different currencies. We handle each case:

• Fee in the quote currency (e.g. USDT) — used directly
• Fee in the traded asset (e.g. you buy ETH, fee charged in ETH) — converted via the trade price. If you’re selling, fee tokens are also a disposal from your pool per CRYPTO22280 — so the disposed quantity increases to include them
• Fee in a third token (e.g. BNB) — converted to GBP at the daily price. If the price isn’t available, the fee is recorded as zero with a warning

Staking & Airdrops

If you upload a Statements CSV (see Supported formats), staking rewards and airdrops are also processed:

• Staking rewards — reported as miscellaneous income at the GBP value on the date received, and added to your Section 104 pool at the same value. Covers earn products, staking interest, referral commissions, and card cashback
• Unsolicited airdrops — added to your Section 104 pool but not treated as income on receipt (CRYPTO22500). Airdrops received in return for a service may be taxable as miscellaneous income (CRYPTO22400). The CGT event happens when you later sell or swap those tokens

How Prices Are Converted to GBP

Every transaction needs a GBP value. The conversion path depends on how the pair is quoted:

1. GBP pair (BTC/GBP) — already in GBP, no conversion
2. Other fiat pair (ETH/USD, SOL/EUR) — converted to GBP at HMRC’s daily exchange rate
3. Stablecoin pair (BTC/USDT) — USDT is mapped to USD, then converted to GBP via the HMRC rate
4. Crypto pair (ETH/BTC) — the quote asset (BTC) is priced in GBP using daily data from CryptoCompare and CoinGecko. The GBP value of the trade is then derived as: BTC amount × BTC/GBP rate

If a price isn’t available for a given date, we check ±1 day. If it still can’t be found, the disposal isn’t valued — instead a Missing prices warning lists the affected coins and dates. You can supply the value yourself: follow the warning to the edit page, find the coin’s row, and enter the GBP value of one coin on the trade date. The disposal is valued on recalculation and the warning clears.

FX Conversions

Why converting currency in your brokerage account is not a taxable event for an individual — and what still is.

If you hold USD in your brokerage account between trades and later convert it back to sterling, that conversion does not create a capital gain. Your cash balance is a debt your broker owes you, and s.251(1) TCGA 1992 puts no chargeable gain on the disposal of a simple debt.

Section 252 takes that exemption away again for foreign currency held with a bank — but only where the account holder is not an individual, a trustee or a personal representative. It was rewritten by Finance Act 2012 with effect from 6 April 2012, and HMRC's own manual now reads that foreign currency bank accounts give rise to gains and losses “for periods up to 5 April 2012”. Before that date the position was the opposite, and the old rules had a narrow “personal expenditure abroad” test — repealed along with s.252A and Schedule 8A.

What is still taxable

The exemption is narrower than “currency is untaxed”. Three things stay in scope:

• The FX inside a share disposal. Buy a US stock in dollars and sell it in dollars, and the gain is still measured in sterling: cost at the exchange rate on the buy date, proceeds at the rate on the sell date. Currency movement between those two dates is taxed — as part of the share gain. We do this automatically on every foreign-currency trade.
• Currency options and futures. The 2012 change explicitly does not reach them. Options appear in your report under Options, not here. Futures are not yet modelled — the report flags them instead of taxing them.
• Physical currency. Banknotes and coin are outside the bank-account rule and keep the old treatment — though currency bought to spend abroad is exempt in its own right (s.269).

Companies are different

None of this applies to a company. Corporate foreign-exchange movements are not capital gains at all — they run through the loan relationships rules (CTA 2009 Part 5) and are taxed as income on the CT600. This calculator produces an SA108 for individuals, so if you are filing for a company, treat the conversions listed in your report as a starting figure for that separate computation rather than a CGT number.

What you will see in your report

Conversions are still read from your statements, pooled and matched, and shown in the FX Conversions section with a running gain or loss. That figure is excluded from your assessment total and from every SA108 box. It is there so you can confirm nothing was missed, and so an accountant filing for a company has the number to hand.

Your broker may label a trade GBP.USD while the report shows USD/GBP. Sterling is your home currency, so it can’t be the asset — the calculator flips the pair to track the foreign side. Selling GBP/USD means acquiring USD; buying it means disposing of USD. Every figure is converted to sterling at the rate on the trade date.

ERI / Offshore Funds

Excess Reportable Income — the extra tax you owe on offshore funds even if you didn’t sell anything. The figures for eight providers are already in the calculator.

What is ERI?

Some offshore funds earn income they never pay out to you — Irish-domiciled ETFs from iShares or Vanguard are the common case. HMRC taxes your share of it anyway, whether or not you sold anything. That is Excess Reportable Income.

Accumulating classes (VWRP, VUAG) reinvest everything, so their ERI is large. Distributing ones (VWRL, VUSA) pay most of it out as dividends, so theirs is small or nil — but if any excess is left, it is still reportable.

How ERI Works

The fund publishes one figure per unit per year, and it lands on your return in two stages:

1. Your pool cost goes up, on the fund’s reporting date — so the same money isn’t taxed again when you sell.
2. The same amount becomes income, six months later — as a dividend or as interest, depending on the fund.

A fund holding more than 60% in bonds or cash pays interest, not dividends. Vanguard says which of its funds are bond funds, so those are treated as interest automatically. For any other provider’s bond fund, add it under Interest Fund Tickers.

Hold 200 shares of VWRP on 30 June 2024, when Vanguard publishes $2.063 per unit at a rate of 0.79: 200 × $2.063 × 0.79 = £325.95. That goes onto your Section 104 pool that day, and is dividend income on 31 December 2024 — so your gain on the eventual sale is £325.95 smaller.

Adding ERI yourself

Needed only when your fund isn’t bundled, or the report names a period we don’t hold. The figure is in the provider’s UK reporting fund status document, one row per share class. Go to Edit → Advanced → Custom ERI Entries and fill in four fields:

Per unit means one share, not your total. We multiply by the shares you held. Hold 500 units, type the £250 total instead of £0.50 per unit, and the report charges you £125,000.

Many rows at once

Paste rows takes a block copied from a spreadsheet or a CSV, one fund and period per line. A header line is fine; the FX rate is optional:

ISIN,Period end,Currency,Per unit,FX rate
IE00BK5BQT80,30/06/2024,USD,2.063,0.79
IE00B4L5Y983,30/06/2024,USD,1.4619
VAGS,30/06/2024,GBP,0.6794

Good lines are added; bad ones are listed by line number so you can fix them.

Changing a figure we applied

The report’s Excess Reportable Income table has an Override link on every fund. It opens this table with the row already filled in — you only change the figure or type your own FX rate. The same funds also sit in the table as grey detected rows, each with a ⋮ menu:

• Override — the row becomes yours to edit. Type a different figure and it turns amber: yours is used instead of ours, the report says so, and the ↵ takes you back to our figure. A row that agrees with ours stays plain, whatever FX rate you give it.
• Delete — no ERI is charged for that fund and period. Use it when you had sold before the period end on a statement you didn’t upload, or your broker already shows the income. The row turns red until you save, then leaves the table; the header shows 1 excluded next to the ⋮ — click either and Restore the ERI for brings the grey row straight back (one period, or all of them at once); save, and the report charges the period again.

Say you sold your 1,000 VAGS on 20 June 2024 but only uploaded this year’s statement. The report still charges £679.40 for 30 June 2024. Delete that period and save: the £679.40 is gone.

Non-reporting funds — taxed as income

Everything above is about funds with UK reporting status. Sell a fund without it — a non-reporting fund — and the gain is taxed as income, not as a capital gain:

• at your income tax rate, up to 45%;
• with no £3,000 allowance;
• a loss stays a capital loss and cannot be set against these gains.

Buy for £8,000, sell for £16,000. In a reporting fund that is an £8,000 capital gain, £5,000 of it taxable after the allowance. In a non-reporting fund the whole £8,000 is income — £3,200 of tax at the 40% rate.

Check the factsheet or HMRC’s reporting funds list — the status belongs to the share class, not the fund, and where the fund is based says nothing. Broker exports don’t show it either, so add the holding under Edit → Advanced → Non-reporting offshore funds.

Hold an offshore fund we have no ERI for and the report asks you to check which it is. An offshore ISIN can belong to a fund or an ordinary share, so where the statement labels its securities (IBKR writes ETF, COMMON, ADR) shares are left alone, and where it doesn’t you get a note rather than a warning.

ERI and the Matching Rules

ERI follows the shares you held on the reporting date, and the calculator splits them for you:

• Pool shares — ERI on your Section 104 quantity on that date.
• B&B shares — a holding sold before the reporting date and bought back within 30 days counts as held, so its ERI is income too. It does not raise the pool cost, because those shares had already left the pool.

Bundled ERI Data

If your fund is in here, its ERI is applied the moment you upload.

Gilts & UK Government Bonds

If you sell a UK gilt, there’s no Capital Gains Tax. There’s also no allowable loss. The rule is symmetric and it’s been the law since 1992.

What a gilt actually is

A gilt is a bond the UK government sells when it needs to borrow. You hand over cash, they pay you a coupon twice a year, and on the redemption date you get your principal back. The Debt Management Office (DMO) does the issuing.

There are two flavours. Conventional gilts have a fixed coupon — 4¼% Treasury Gilt 2032 pays 4.25% of nominal twice a year until March 2032, then redeems. Index-linked gilts uplift both the coupon and the principal in line with RPI. Both kinds are exempt from CGT.

Why no CGT

Section 115 of the Taxation of Chargeable Gains Act 1992 says it directly: a disposal of a gilt-edged security isn’t a chargeable disposal.

The exemption is just for the sale. The interest the gilt pays you — the coupon — is still taxable as savings income. If you sell between coupon dates, the accrued interest goes on your return separately under the Accrued Income Scheme.

How we know it’s a gilt

We match by ISIN against a list of every gilt the DMO has issued. The list is in the codebase — view it here — sourced from DMO’s own data feed and snapshotted from 2022 onwards so historical disposals work too.

ISIN prefixes alone aren’t enough — GB00B* also shows up on UK corporate bonds and even UK equities. The only reliable signal is the exact ISIN against the issuer’s register.

If you see “UK bond not in registry”

This warning appears when your broker reports a bond disposal with a GB-prefixed ISIN that isn’t in our list. Two possibilities:

1. It’s a UK corporate bond. Those are taxable like any other share. Leave the calculation alone — the warning is just asking you to confirm.
2. It’s a gilt we don’t recognise yet. Either a very new issue (after our last DMO refresh) or a very old one (redeemed before our snapshots start in 2022). Cross-check the ISIN against the DMO website. If it’s a gilt, remove the disposal manually before exporting your return — or open a ticket so we add it to the registry.

Either way the safe default is to treat it as a normal share — you might overpay on a gilt we missed, but you can’t accidentally underpay.

What this chapter doesn’t cover

If you only hold gilts, skip the rest — you’re done. The list below is for completeness.

• UK Treasury Bills are short-term Treasury paper, under a year. Different report at DMO, handled separately.
• Gilt strips are zero-coupon securities created by stripping a gilt into its component cashflows. Different tax treatment in detail. Not in v1.
• Gilt futures and options are derivatives. Different rules, handled by the options pipeline.
• Foreign government bonds — US Treasuries, Bunds, JGBs — are taxed normally under UK CGT, with any treaty relief claimed separately.

Dividends & Interest

How dividend income and interest income are taxed, including allowances and double taxation relief.

Dividend Tax

Dividends from UK and foreign shares are taxed at special rates, separate from your normal income tax. You get a tax-free dividend allowance each year:

After the allowance, dividends are taxed at:

Here is how the calculation works:

Foreign Dividends

Foreign dividends are converted to GBP at the exchange rate on the payment date. When a country withholds tax at source, the UK has treaties that let you offset some or all of that withholding against your UK tax bill.

Treaty relief is calculated automatically for supported countries:

This relief is formally Foreign Tax Credit Relief (FTCR), capped at the UK tax on the same dividend:

You claim it on the Foreign pages (SA106) of your Self Assessment — see Report output for the box-by-box mapping.

Dividend reinvestment (DRIP): When dividends are automatically reinvested in shares, the calculator counts the dividend as income and the reinvested shares as a stock purchase — both are tracked separately for tax purposes.

Capital gain distributions: Some funds distribute capital gains to shareholders. These are treated as dividend income for UK tax purposes and included in your dividend total.

Interest Income

Interest earned on cash balances at your broker is taxed at your normal income tax rate. You get a Personal Savings Allowance (PSA) that depends on your tax band:

Note: Interest is grouped by month and broker in the report for easy cross-referencing with your broker statements. Deeply discounted securities are the exception — each instrument gets its own named row.

Interest fund tickers: Some funds pay interest-like distributions that your broker labels as dividends. If you hold such funds, you can add their ticker symbols in the Settings panel under Interest Fund Tickers. Their income will then be taxed at interest rates instead of dividend rates. Vanguard’s bond funds are recognised by their ISIN, so you only need to add other providers’ funds.

Non-reporting offshore funds: A gain on selling a non-reporting offshore fund is taxed as income (an “offshore income gain”) rather than a capital gain — at income rates, with no annual exempt amount. A loss is not an offshore income loss, but it stays an allowable capital loss. If you hold such funds, add their ISIN (preferred, since a ticker can collide across exchanges) or ticker in the Settings panel under Non-reporting offshore funds. The gain goes in box 41 of the SA106 Foreign pages (“Gains on disposals of holdings in offshore funds”) — the amount of the gain, not the tax on it — and the filling guide shows the figure to copy. See ERI / Offshore Funds for details, or HS265 for HMRC’s own guidance.

US Treasury bills (T-bills): Held-to-maturity T-bills are Deeply Discounted Securities. The discount earned at redemption is income, not a capital gain, and it counts as savings income — so it gets the Personal Savings Allowance and the savings rates (SAIM1080). A US issuer makes the discount relevant foreign income, which goes on the SA106 Foreign pages (SAIM3070); SA101 box 3 is for UK deeply discounted securities such as gilt strips. The calculator detects T-bills in Schwab, IBKR and Fidelity exports and lists each one as its own interest row, tagged DDS — no manual flagging required.

Accumulation units

An accumulation (“Acc”) fund does not pay its income out — it reinvests it, so your units simply become worth more. HMRC still treats that reinvested income as taxable income in the year it is reinvested. In return, the same amount is added to the cost of your units (HMRC CG57707), so you are not taxed on it a second time as a gain when you sell.

Equalisation is the part of the first reinvestment after you bought that was already included in your purchase price. It is not income, so it is taken off before the income is taxed. If your voucher shows no equalisation, enter only the accumulation.

How to enter it

1. Take the figures from your fund manager’s tax voucher or your platform’s consolidated tax certificate. In an AJ Bell export they are the Accumulation Distribution and Equalisation Acc Units rows.
2. On the Edit page, add a transaction with the Accumulation action — fund, date and £ amount. Add an Equalisation row with the same fund and date if your voucher shows one. In a Generic CSV the actions are ACCUMULATION_DISTRIBUTION and EQUALISATION.
3. For a money-market or bond fund, add its ticker under Advanced › Bond / Interest Fund Tickers so the income is taxed as interest. Otherwise it is taxed as dividends.

The report tags these rows Accumulation in the income table and shows the cost uplift in the pool history. This applies to UK funds only: an offshore fund (non-GB ISIN) reports its reinvested income as Excess Reportable Income instead.

Annual income

Interest and dividends are taxed on top of your other income — so the tax on the same interest depends on how much you already earn. This applies to all your interest and dividends (broker cash interest, foreign interest, fund distributions and the T-bill discount), not just one source.

Your band is set by your total income (salary + interest + dividends). The thresholds:

If interest crosses a threshold, the part above is taxed at the next rate. Below, two people earn the same £2,000 of interest but pay different tax — only because their salaries differ:

That is why we ask which band you are in: without it we cannot tell whether your interest sits in the 20%, 40% or 45% band, so the report shows every band and you pick your own. The Tax Profile tab gives you two ways to get a single figure instead. A tax code (like 1257L) does not help — it only states your tax-free allowance, not your total income.

Pick a band, or enter your income

Select a band (Basic / Higher / Additional) if you would rather not disclose the exact figure. Picking a band still tells us something precise: it caps your total income, and we already know the investment part of that total from your transactions. Subtract one from the other and your remaining income has a known ceiling — so we charge you as if you earned exactly that, which is the most anyone in your band could owe. The result is labelled approximate throughout the report, because it is an upper bound rather than your actual bill.

Where that ceiling is low enough, the reliefs stop being guesswork and we apply them in full. A Basic-rate filer with £12,000 of interest and £30,000 of dividends cannot have more than £8,270 of other income, which is under the personal allowance whatever the true figure — so the starting rate for savings and the unused allowance both apply, and the bill is £2,921.25 rather than the £4,781.25 that flat band rates would charge. Three rules still need the actual number when the ceiling is too high to force them:

• Starting rate for savings. If your non-savings income is below £17,570, part of your interest is taxed at 0% (ITA 2007 s12). With a small portfolio the band leaves room for far more income than that, so we cannot tell whether you qualify and the figure over-states your tax — someone on a £15,000 salary with £3,000 of interest owes £0, but the Basic band figure shows £400.
• Unused personal allowance. If your income does not use up the £12,570 allowance, the remainder shelters your investment income. Again a small portfolio leaves the ceiling too high to prove it: £5,000 of salary plus £2,000 of staking rewards owes £0, but the Basic band figure shows £400.
• Band straddle. Where your income lands inside the band changes which slice of your interest or dividends crosses a threshold. We assume the top of the band, so the split is the least favourable one available to you.

Because the band is read as a statement about total income, picking one that is too low now shows as an error rather than a quietly cheaper bill: if your interest and dividends alone exceed the band’s ceiling, no such taxpayer exists and the report says so.

Enter your income for the exact figure and the precise marginal split is computed instead. The two are one choice, not two settings: picking a band clears any income you had entered, and entering an income clears the band. Choose Rather not say to go back to the every-band table.

What to enter

Your other taxable income for the year, before this year’s interest and dividends:

If none of that applies to you — no salary, no pension, no rent — enter 0. That is a real answer, not a blank, and it is the case where entering the figure helps most: with nothing using up your £12,570 personal allowance, it shelters your interest and dividends instead, and the bill is often nil. No band can tell us that.

What changes in your report

• The tax-band badge changes from “All bands” to your band (e.g. “Higher rate”). When you picked the band rather than entering income, hovering the badge notes the figure is approximate.
• The three-row Tax by Income Band table becomes a single Income Tax Due figure, using the right tax-free allowance for your band.
• Your Capital Gains Tax is unchanged — neither your income nor your band affects it.

Residency Status

How your UK tax residency affects which disposals are subject to Capital Gains Tax.

If you were a UK resident for the entire tax year, you don’t need to configure anything — the calculator treats you as fully resident by default. But if you left the UK, returned from abroad, or spent part of the year as a non-resident, your residency status determines which disposals are subject to CGT and which are excluded.

How It Works

You define one or more residency periods in the Settings panel, and the calculator checks each disposal against them to decide if it’s taxable.

There are three residency statuses:

Taxability Rules

Taxability depends on both when you sold and when you acquired the shares:

HMRC’s anti-avoidance rules prevent you from leaving the UK briefly to sell assets tax-free.

Effect on Share Matching

Residency status also affects how HMRC’s share matching rules work:

• Same Day Rule — still applies, but the taxability of the match depends on your residency at disposal
• Bed & Breakfast Rule — has a special exception: if you were non-resident when you reacquired shares (after 22 March 2006), the B&B rule doesn’t apply to that match
• Section 104 Pool — non-taxable matches still consume shares from the pool but don’t generate a CGT entry

Mixed-Year Residency

If you were resident for part of the year and non-resident for the rest, the calculator handles each disposal individually based on its date. Your report will show:

• A “Mixed residency” status indicator in the summary
• The number of days spent as resident vs non-resident
• A separate table of excluded disposals showing each sale that fell outside your UK-resident periods, with the gain or loss that was excluded

Configuring Residency

Open the Settings panel (gear icon) and switch to the Residency Status tab. Add a period for each time your status changed:

• Start date — when this status began (required)
• End date — when this status ended (leave blank if ongoing)
• Status — Non-Resident or Temporary Non-Resident

You only need to add periods where you were not UK resident. Any dates not covered by a period are treated as UK resident by default. Your residency configuration is saved in your browser and applied automatically to future calculations.

Salary Calculator

A free take-home pay calculator for the 2024/25, 2025/26 and 2026/27 tax years. It is separate from the CGT report — nothing to upload, no sign-in, and it runs entirely in your browser.

What it deducts

Everything is computed from the published thresholds for the tax year you pick — the rate tables on the page itself show the exact figures used. Tick Resident in Scotland and the income tax section switches to the Scottish bands; NI and student loans are the same UK-wide.

Reading the results

The headline figure is annual take-home, with monthly and weekly alongside. The table beneath explains the gap: gross salary, then each deduction, then the total taken. The diagram draws the same split to scale — the wide band is what you keep.

Below the table, two lines place you against HMRC’s income distribution — the share of UK taxpayers who earn less than you, and the share who pay less Income Tax. Both come from the Survey of Personal Incomes for 2023/24, the latest year HMRC has published.

What it deliberately leaves out

The result is an annualised estimate for a standard tax code. Bonuses, benefits in kind, net-pay-arrangement pensions and Marriage Allowance are not modelled. For relief-at-source pensions the calculator shows payslip-level tax: higher-rate taxpayers reclaim the extra relief through Self Assessment, and that reclaim is not folded into the numbers.

Sharing a calculation

The inputs are mirrored in the URL. /salary-calculator?salary=110000&pension=10 opens with £110,000 and a 10% salary-sacrifice pension already applied — useful for sending someone the exact scenario you are looking at. Anything else in the link, such as campaign tags, is left untouched.

Once you know your take-home

A monthly take-home figure is the input most people actually want a mortgage payment measured against, so the Mortgage Calculator sits next to this one and works the same way — nothing to upload, no sign-in. If you also sold shares, funds or crypto during the year, the CGT rate you pay turns on the taxable income this page gives you; the CGT report takes it from there.

Open the Salary Calculator →

Mortgage Calculator

A free mortgage repayment calculator. It is separate from the CGT report — nothing to upload, no sign-in, and it runs entirely in your browser.

What the inputs mean

Every figure is computed month by month in exact pence — the same simulation drives the headline stats, the cost table and the chart, so they always agree.

What it deliberately leaves out

Stamp Duty Land Tax, product and arrangement fees, valuation, legal costs and insurance are not modelled — the result is the loan arithmetic only. The rate is assumed constant for the whole term; when a fixed deal ends, recalculate with the new rate.

Sharing a calculation

The inputs are mirrored in the URL. /mortgage-calculator?price=350000&rate=5&term=30 opens with a £350,000 purchase at 5% over 30 years already applied. Anything else in the link, such as campaign tags, is left untouched.

Working out what you can afford

A lender cares about what lands in your account, not your gross salary. The Salary Calculator gives you the monthly take-home figure to hold the payment above against — Income Tax, National Insurance, pension and student loan taken off.

Open the Mortgage Calculator →

Buy-to-Let Calculator

A free buy-to-let profitability calculator. It is separate from the CGT report — nothing to upload, no sign-in, and it runs entirely in your browser.

What the inputs mean

Section 24 — why higher-rate landlords pay more

Since April 2020 an individual landlord cannot deduct mortgage interest from rental income. The tax is charged on the full profit and then cut by a credit worth 20% of the interest. A basic-rate taxpayer ends up where the old rules left them; a higher- or additional-rate taxpayer does not, because the profit is taxed at 40% or 45% while the interest is only relieved at 20% — which is why a mortgaged buy-to-let can show a profit on paper and still lose money each month.

Personal or a limited company

Switch the ownership toggle to compare the two. A company deducts mortgage interest in full and pays Corporation Tax on the profit — 19% up to £50,000, 25% above £250,000, with marginal relief in between — and Section 24 does not apply. The tool does not model the further tax on taking the profit out of the company as dividends, so treat the company figure as pre-extraction.

What it deliberately leaves out

It models a single property. It covers the purchase tax in all three nations (SDLT, LTT and LBTT) and, for Scotland, an approximate mapping of the Scottish Income Tax rates. For a company it stops at Corporation Tax and does not model dividend extraction, associated-company scaling of the profit limits, HMOs, holiday lets, or refurbish-refinance strategies. The figures are a year-one snapshot at today’s rate — a planning estimate, not tax advice.

Total return and capital growth

Rental cashflow is only part of the story. The projected-growth input applies to the whole property value, so with a mortgage it is geared against the cash you actually put in: at 2% a £250,000 property gains £5,000 a year, which on a £79,000 deposit-and-costs stake is worth far more than 2% on your money. The total return adds that capital growth to the post-tax cashflow over the cash invested. It is a first-year assumption, not a guarantee — set it to 0 to judge the deal on cashflow alone, or go negative to stress a downturn.

Sharing a calculation

The inputs are mirrored in the URL. /buy-to-let-calculator?price=200000&rent=1100&band=higher opens with a £200,000 purchase let at £1,100 a month for a higher-rate landlord already applied. Anything else in the link, such as campaign tags, is left untouched.

When you actually sell

For the Capital Gains Tax on a real disposal — with private-residence and letting relief, the annual exempt amount and your remaining basic-rate band all applied — use the main CGT calculator.

Open the Buy-to-Let Calculator →

Retirement Calculator

A browser-only FIRE projection for estimating a spending target, possible timing and the monthly saving needed for a chosen age.

Calculation contract

The target is annual spending divided by the withdrawal rate and is rounded upward to a penny. Monthly real growth uses ((1 + return) × (1 − fees) ÷ (1 + inflation))^(1/12) − 1. Growth is rounded to pence before each month-end contribution is added.

The target-age solver searches whole-penny monthly contributions and returns the lowest amount whose projection reaches the target. If the target age is today, it reports a capital shortfall instead; if the supported contribution ceiling is insufficient, it says so rather than returning a capped answer.

Important limitations

The deterministic estimate does not model sequence-of-returns risk, tax, State Pension, pension access rules, defined-benefit income or changing spending. A 4% withdrawal rate is a guideline rather than a guarantee, and investments can fall as well as rise.

Open the Retirement Calculator →

Compound Interest Calculator

A free savings and investment growth calculator. Nothing is uploaded or stored, no sign-in is needed, and every calculation runs in your browser.

What the inputs mean

The projection is simulated month by month in integer pence. Its headline figures, growth chart and yearly table all use the same schedule.

What it deliberately leaves out

The result is before tax and costs. It does not compare ISA, pension or General Investment Account wrappers, and it does not deduct Capital Gains Tax, dividend tax, fund charges, dealing costs or platform fees. Reduce the return assumption if you want to allow approximately for recurring costs.

Open the Compound Interest Calculator →

Privacy & Security

Your financial data is sensitive. Here’s exactly what happens to it — and what doesn’t.

How Your Data Flows

Your broker file travels over an encrypted connection to our server, where it is processed entirely in memory — never written to disk or saved to any database.

When you upload a broker CSV, four things happen — all in memory on our server:

1. Your file is received — the CSV is parsed in memory. It is never written to disk.
2. Exchange rates are applied — HMRC’s official monthly rates convert foreign-currency trades to GBP.
3. The engine calculates your report — all matching rules, option strategies, corporate actions, and income calculations run in memory.
4. You see the result — the finished report is sent back to your browser and rendered on screen. You can download it as a PDF, and nothing is kept afterwards.

Data Storage by Tier

On every plan, your CSV is sent to our server for calculation, processed in memory only, and never stored.

When a report is saved to your reports list, the statements it was built from are kept in your browser’s own storage beside it, so a statement you add later on the Edit page is read together with them. They stay on your device, are never sent anywhere the report itself is not, and are deleted with the report.

Firms that cannot send client files to a third party at all can have a dedicated deployment on the Business plan, where the engine runs in the browser and files never reach us — see Private Instance.

The taxpayer name, UTR and broker you can put on a report (see Your Name and UTR on the PDF) never leave your browser at all. They are kept there, on the one report they belong to: they are not part of any calculation request, they are in no analytics event, and they are never logged. The PDF and the CSV are both built on your own device, so putting your name on either sends us nothing. The tax engine never sees them, so they cannot change a single figure — they are labels on a document.

Because they belong to that one report, there is deliberately no “remember this for next time” setting anywhere in the product: filling them in for one client can never pre-fill or leak them onto another client’s report. Clearing the section removes all three at once, and deleting the report from Recent deletes them with it. And because your browser is where they live, they are on that device only — a different browser, or one whose data you have cleared, has no copy.

Analytics & Cookies

We use Vercel Web Analytics to understand how many people visit the site. It collects page views and country-level geography — no personal data, no IP addresses, no fingerprinting. It is privacy-compliant by design and does not use cookies for tracking.

We do not use Google Analytics, Facebook Pixel, or any advertising tracker.

What We Don’t Do

• We do not sell or trade your data, and we do not share it with advertisers or data brokers
• We do not store your broker files, transaction history, or calculated reports
• We do not receive the taxpayer name, UTR or broker on your report — they stay in your browser
• We do not use advertising cookies or tracking pixels
• We do not fingerprint your browser or device

If You Sign In

Sign-in is only needed for paid tiers. If you sign in with Google, two pieces of information end up on file:

• Your email and display name, taken from the Google sign-in token
• An internal account ID, the date you signed up, and the date you last logged in

That is the entire record, and none of it is linked to your trades or reports.

The legal basis is contract performance (Article 6(1)(b) of the UK GDPR): we need this much to run the account.

Who Else Touches Your Data

A short list of services involved in running the site:

• Supabase — holds the sign-in record (EU region, encrypted at rest and in transit)
• Google — runs the OAuth sign-in itself (US, transfers covered by Standard Contractual Clauses)
• Vercel — hosts the site and runs the cookieless analytics described above

If we add or change any of these, this page is updated.

How Long Things Are Kept

The sign-in record lives as long as the account does. Ask us to delete the account and it goes too. Supabase keeps short-term backups for service recovery, typically a few days.

If you have never signed in, there is no record of you to keep or delete.

Your Rights

Under UK and EU data protection law you can ask us to:

• Show you what we have on file (it’s only what’s listed under “If You Sign In”)
• Correct anything that’s wrong
• Delete the account and the record with it
• Send you a copy as a JSON export
• Stop processing it

Email support@cgtcalculator.io and say what you need. Mention the email address you signed in with so we can find the record. We reply within 30 days under the GDPR clock, usually much sooner. There is no form to fill in.

If you think we mishandled your data, you can also complain to the UK Information Commissioner’s Office at ico.org.uk.

Private Instance

If sending client files to a third party is not an option, we can run the calculator on a separate instance where your broker files never reach our servers.

How It Works

The calculation engine is compiled to WebAssembly (WASM) — a format that runs natively in your browser, just like JavaScript, but faster. On a private instance it is the browser that parses your broker files and applies every matching rule, so the files themselves stay on the machine that opened them.

What Still Travels

Your transactions stay on your device. Three things still cross the network, and none of them carry your trades:

• Exchange rates — HMRC’s official monthly rates, so foreign-currency trades can be converted to GBP
• Crypto prices — looked up per coin and date, if your report includes cryptoassets
• Your sign-in — the account and licence check that unlocks the plan

You can confirm this yourself: open your browser’s Network tab (F12 → Network) while generating a report. You will see those requests and the WASM binary itself — and no request carrying your trades, positions, or amounts.

Who It Is For

Accountancy practices and platforms that handle other people’s financial data, where the question is not whether you trust us but whether you are permitted to send client files anywhere at all.

On the public site every plan calculates on our server, in memory, and nothing is stored — see Privacy & Security for what that involves. A private instance changes where the calculation happens, not what we keep.

To ask about it, email partnerships@cgtcalculator.io or use our contact page.

How Long It Runs

A private instance is set up for a period agreed with you when we scope the deployment, and can be renewed at the end of it. It is not a permanent parallel service: if the agreed period ends without renewal, we retire the deployment and your licence goes back to the public site.

Retiring an instance puts none of your work at risk. Nothing of yours lives on it — no broker files, no transactions, no reports — so there is nothing to migrate out and nothing left behind to delete.

Where Your Data Goes

Subscription & Refunds

The paid plan is a yearly subscription. Here’s how billing, cancelling, and refunds work.

What You Get

The free plan (Museum) runs a small report on our server. The paid Investor (“Fish & Chips”) and Business (“High Tea”) plans unlock the full per-trade report, PDF export, options and fund handling, and unlimited disposals. Each includes a set number of report generations per year — more on Business, which can also buy top-up packs. The current prices are on the pricing section.

Billing

Renewal is automatic, once a year. If the price ever changes, we email you first and you can cancel before it takes effect. Payment goes through Stripe; we never see or store your card.

Cancelling

Cancel from the Subscription tab in your account. From there:

• Access stays full until your renewal date — the end of the period you’ve already paid for
• After that the plan drops to Free and nothing renews — no more charges

Refunds

Two ways a refund applies:

The change-of-mind refund closes once you open the paid report — it unlocks on payment, so opening it counts as using it (your right under the Consumer Contracts Regulations 2013). Unsure? Run the free plan first. If something is genuinely broken on our side, we’ll fix it or refund you any time, opened or not — send the file with the “Send report” button so we can check.

Full legal wording is in the Terms.