Frequently Asked Questions

Capital Gains Tax, or CGT, is the tax you pay on the profit when you sell shares or other investments for more than they cost you. The important thing is that you're taxed on the gain — the profit — and not on the whole amount you receive. So if you bought shares for £1,000 and sold them for £1,500, it's the £500 of growth that counts. How much you pay depends on your income tax band, and the rates on shares changed partway through 2024: up to 30 October 2024 they were 10% for basic-rate taxpayers and 20% for higher and additional-rate taxpayers; from 30 October 2024 onwards they rose to 18% and 24%. GOV.UK covers the basics and lists the current CGT rates.

No, you can leave those out. ISAs and SIPPs are tax-sheltered accounts, which means any profit you make inside them is completely free of Capital Gains Tax — so they don't belong in a CGT calculation at all. Just enter the trades from your ordinary, taxable accounts. If you'd like to read more about how ISAs work, GOV.UK has a good overview.

No — this calculator is just for shares and securities. Residential property plays by a different set of CGT rules, with reliefs like Private Residence Relief (which can wipe out the tax on your main home), letting relief, and its own tax rates. Those aren't covered here, so a property sale needs a property-specific calculation. HMRC's Private Residence Relief helpsheet (HS283) is a good place to start.

Yes. HMRC taxes most crypto in much the same way as shares: your holdings of each token are pooled, and the same same-day and 30-day cost rules apply when you work out the cost of what you've sold. That means the calculator's matching logic fits crypto disposals well — just enter your buys and sells as you would for any share. To check the details for your own situation, see HMRC's cryptoasset guidance.

That's fine — it still works. The CGT matching rules don't care whether a share is listed on a stock exchange, so unlisted or private company shares are handled in exactly the same way. Just enter the trade details — date, quantity, and price — as you would for anything else.

Every UK tax year from 2008/09 right through to 2026/27. Remember the UK tax year is a little unusual — it runs from 6 April to 5 April the following year, rather than matching the calendar year. Anything before 6 April 2008 isn't supported.

Those aren't supported directly, but there's an easy workaround. The calculator starts from the 2008/09 tax year, so if you have older trades that feed into your Section 104 pool — the running pot that tracks the average cost of shares you still hold — you can work out that pool's balance up to April 2008 yourself, then enter it as a single buy at that cost. From there, the calculator takes over.

It applies HMRC's share matching rules for you, in the exact order HMRC requires: the same-day rule first, then the bed and breakfast (30-day) rule, and finally your Section 104 pool. All the number-crunching happens right in your browser, so your trade data never leaves your device. The only things that ever reach a server are the optional exchange-rate and stock-price lookups, and even those send just a currency code or a ticker symbol — never your figures (there's more in the Privacy section below). The engine doing the sums is open source, so the logic is there for anyone to inspect.

The Annual Exempt Amount is your tax-free allowance for capital gains — the slice of profit you can make each year before any CGT is due. For 2024/25 onwards it's £3,000 (it was more generous in earlier years). You only pay tax on gains above it, and it's use-it-or-lose-it: if you don't use the allowance in a given year, you can't carry it forward to the next. You can check the current figures on GOV.UK.

Each year's summary tells you whether HMRC is likely to expect a report — but treat it as a helpful nudge, not the final word. As a rule, you need to report if your gains are above the tax-free allowance, or if your total sale proceeds for the year are more than £50,000 (for years before 2023/24 the proceeds threshold was four times the allowance), even when there's no tax to pay. The calculator flags this so nothing catches you out. GOV.UK explains when you must report and how to report and pay.

It's a planning helper — and one you'll only find here — that suggests roughly how many shares you could sell to use up the rest of your tax-free allowance for the year. One thing worth knowing: it works from the average cost in your Section 104 pool, so it doesn't try to model the same-day or 30-day rules. Treat its suggestion as a sensible starting point, then add that trade and re-run the calculator to see the figure that actually counts.

Yes. Once you've run a calculation, you can download a full PDF report — handy for your records or to hand to an accountant — or export your data as CSV or Excel. And because nothing is saved on our side, that export doubles as your safety net: keep the file, and next year you can re-import it and simply add the new year's trades on top.

However suits you best. You can upload a CSV, TSV, or Excel file from your broker, paste rows straight from a spreadsheet, type trades in by hand, or load the built-in sample data to see how everything works first. Whichever route you pick, you go through three simple steps: import your trades, review them (the calculator flags anything that looks off, like selling more shares than you held), then calculate.

Each row is a single trade, with these fields: date, type (buy, sell, transfer, or split), symbol, quantity, unit price, fees (your allowable expenditure), currency, and exchange rate. Don't worry about getting the layout perfect — the import step lets you match your spreadsheet's columns to these fields and shows you a preview before anything is calculated. Foreign-currency trades are fine too; just include the currency, and either add the exchange rate yourself or let the tool fetch HMRC's rate for USD and EUR.

Enter the vest as a buy, priced at the shares' Fair Market Value (FMV) on the day they vested. That FMV becomes your cost basis — the figure your future gain is measured against — which is exactly what HMRC expects for shares you received through work. Use the full number of shares that vested as the quantity.

Enter it as two trades on the vest day. First, a buy for the full number of shares that vested, priced at their Fair Market Value (FMV). Then a sell, on the same day and at the same FMV, for the shares that were sold to cover your tax. Because the two share a date and price, the same-day rule matches them with no gain, and the shares you kept simply settle into your Section 104 pool at the FMV cost.

You've got two options. Since selling everything on the vest day leaves you with no shares and essentially no gain, you can simply skip these entirely. Or, if you like keeping a complete record, enter a matching buy and sell at the same price — just note there may be a small loss from the fees if you choose to include them.

It handles plain stock splits. Add a trade with the type set to split, and the calculator adjusts the number of shares in your pool while keeping your total cost the same — so a 2-for-1 split doubles your share count without changing what you paid. More involved corporate actions, like rights issues, bonus issues, mergers, or returns of capital, aren't modelled automatically; for those, work out the adjusted figures and enter them as ordinary trades.

Gifts of shares between spouses or civil partners are treated as no gain, no loss — meaning the transfer itself never creates a tax bill for the person giving them away (this is set out in s58 TCGA 1992). Instead, your partner takes the shares on at your original cost, so any future gain lands on them when they eventually sell. In the calculator, just add the shares as a transfer; it figures out exactly which shares moved (using the same-day and 30-day matching rules) and what cost travels with them, and records the gain as zero. HMRC cover this in their Capital Gains Manual.

It's by design, because a spouse transfer is always no gain, no loss. The unit price you enter makes no difference to the result, so you can leave it as anything. Fees are treated as zero too, because HMRC doesn't let you deduct the costs of transferring shares between spouses or civil partners.

Enter the rate as units of foreign currency per £1 — the same convention HMRC uses. So if £1 buys 1.27 US dollars, you would enter 1.27. To save you looking it up, there's an “HMRC” button next to the exchange-rate field that fetches HMRC's official monthly rate for you.

The calculator can automatically fetch HMRC's official monthly rates for US Dollars (USD) and Euros (EUR), across every supported tax year from 2008/09 onwards. For any other currency, just enter the rate by hand — as units of foreign currency per £1. You'll find the official figures on the HMRC exchange rates page.

No, and you won't need it. Taper Relief was scrapped from 6 April 2008, and since the calculator only covers tax years from 2008/09 onwards, it simply doesn't come into play.

No. Indexation Allowance — an old relief that adjusted gains for inflation — was frozen at December 2017 and then removed for individuals on disposals after 1 January 2018. The calculator doesn't apply it.

No. This was part of the old Taper Relief system, which no longer applies to disposals from April 2008 onwards, so it isn't relevant to the years this calculator covers.

Not automatically. The calculator works out the gains and losses for each tax year on its own, and doesn't carry losses forward from one year into the next — so you'll need to bring forward any earlier losses yourself when you complete your self-assessment. GOV.UK explains how capital losses work and how to claim them.

No. BADR — which used to be called Entrepreneurs' Relief — gives a reduced CGT rate when you sell all or part of a business, but it depends on specific qualifying conditions that sit outside what this calculator does. You can read the rules on GOV.UK.

No — it's built purely for shares and securities (cryptocurrency included). Property, and other kinds of assets like art or collectibles, follow different rules and aren't covered here.

Nowhere — it stays on your device. All the number-crunching happens in your browser, so the shares, dates, and prices you enter are never sent to us or saved to a database. Close the tab and it's gone; there's no account and nothing left behind. The only thing remembered between visits is whether you chose light or dark mode, which sits in your browser's local storage and isn't shared with anyone. The privacy page has the full details.

Only the bare minimum, and never anything financial. If you ask for an exchange rate, it sends just a currency code and a date to a small server-side helper that looks it up from HMRC or a public rates source. If you ask for a stock price, it sends only the ticker symbol (like AAPL) on to Yahoo Finance. Neither lookup ever sees your quantities, your costs, or your gains — and both are completely optional, so you can type every figure in by hand if you'd rather not use them.

No tracking, no analytics, no advertising — none of it. The app itself doesn't set any cookies. The one honest caveat is housekeeping: the site is hosted on Cloudflare, which may set its own strictly-necessary cookies to keep things secure and running, and that's outside our control. There are no marketing or profiling cookies anywhere. The privacy page spells it all out.

No on both counts. This is an independent tool, not connected to HMRC or any tax authority, and it doesn't give tax advice — it does a calculation to help you understand your position. For anything that affects what you actually file, check the official guidance on GOV.UK or speak to a qualified accountant or tax adviser. The full wording is in the terms.

The part that matters most is. The calculation engine — the code that actually applies HMRC's matching rules and works out your gains — is open source on GitHub, so you (or your accountant) can read it and check it line by line. The website around it isn't open source, but the engine that does the sums is fully out in the open.

No account, no sign-up, and no ads. You don't hand over an email or create a login to use anything here — just open the calculator and go. And you'll never see an advert or a premium upsell; the whole thing is free to use.

Honestly? It doesn't. There are no ads, no fees, and nothing to buy — it's free, and it's built and maintained by one developer in their own time. The only thing keeping it online is the kindness of people who chip in through GitHub Sponsors, which covers the hosting bills. If the tool saved you a headache and you'd like to help keep it running, the support page explains how — but it's completely optional, and the calculator will always be free either way.

Just get in touch — I'd genuinely like to hear about it. The quickest way is the contact page, where you can email contact@capitalgainscalculator.app. It really helps to know what you did, what you expected, and what actually happened — and a small bit of sample data that reproduces the problem is gold. If the bug is specifically in the open-source calculation engine, you're also welcome to raise it on the engine's GitHub repo.

Ideas are always welcome. Head to the contact page and send a note describing what you'd like and the situation it would help with — real examples make it much easier to build the right thing. I read every message, even if I can't get to everything straight away.