Short answer: whatsmycgt is a well-presented free calculator. It applies the same-day, 30-day and Section 104 rules, gives SA108 box figures and an audit trail, and runs in your browser. If your trades fit one spreadsheet in pounds, it may be all you need. FiscalFox is a paid report built for messier records: original exports from many brokers, foreign currency, automatic ERI, corporate actions, share plans, and a report pack an accountant can check.
Checked on 12 October 2026 against whatsmycgt.co.uk (the calculator page, its FAQ, privacy policy and terms). Free tools change often, so check the site for anything that matters to you.
FiscalFox vs whatsmycgt at a glance
| Area | FiscalFox | whatsmycgt |
|---|---|---|
| Price | Calculation preview is free. Report pack £39.99 per tax year, paid once. Optional done-for-you report £100. | Says it is free forever, with no sign-ups, subscriptions or hidden charges. |
| Share matching | Same-day, following 30 days, then the Section 104 holding, across all imported accounts. | Same-day, 30-day bed and breakfast, then Section 104 pool, applied to every disposal. |
| Getting your trades in | Reads original exports from 18 named brokers, plus an AI import for other layouts. | An Excel, CSV or ODS file with date, ticker, buy or sell, quantity, price and fee columns. It names Trading 212, Freetrade, IBKR, HL, AJ Bell and Schwab and says most exports work with minimal adjustment. |
| Foreign currency | Converts each non-sterling trade at the Bank of England daily rate for its date (European Central Bank rate as a backup) and shows the rate used. | Prices and fees must be converted to pounds before you upload. |
| ERI on offshore funds | Spots reporting funds from the ISINs in your export and adds published ERI to the pool cost automatically for funds it holds figures for. A missing figure is not treated as zero. | You enter the report date, ERI per share and distribution date for each fund; it works out your holding and adds the ERI to the pool cost. |
| Corporate actions | Researches splits, consolidations, spin-offs, mergers and share class changes against published sources, checks them against your holdings and asks you to review anything it cannot confirm. | You enter share splits, reverse splits and consolidations, and it adjusts the pool. |
| RSUs, ESPP, options and crypto | Reads Charles Schwab Equity Awards and Morgan Stanley StockPlan Connect history, supported option rows, and a Koinly Capital Gains Report for crypto. | The site does not describe these. |
| Tax figures | Applies the annual exempt amount, losses you bring forward and the CGT rates to estimate the tax due, with SA108 figures for published filing years. | SA108 box figures for each tax year. You enter your CGT rate; the annual exemption defaults to the selected year. |
| Output | On-screen workings free. Paid PDF and CSV report pack with every disposal, Section 104 pool workings and Self Assessment working papers. | An audit trail of every disposal and the rule used, P&L charts, a sell simulator, and copy, .txt or CSV export. |
| Your data | Built-in imports are read in your browser where possible. Saving work needs an account, and some features (the AI import and corporate action research) send data to AI providers, as the privacy policy explains. | Says everything runs in your browser, with no servers, databases or accounts, and that your data is discarded when you close the page. |
What whatsmycgt does well
whatsmycgt covers the core of a UK share calculation without asking you to sign up or pay. It applies the three matching rules, shows which rule matched each disposal, and maps the result to SA108 boxes for each tax year. It lets you add ERI, share splits and dividend income by hand, warns about rows that look like duplicates, and has a sell simulator that uses your Section 104 cost to show the tax effect of a sale before you make it.
Its privacy position is simple: it says your trade data never leaves your device. If that is your first priority, it is a real strength.
When whatsmycgt is probably enough
- Your trades are already in pounds, for example UK shares and sterling-priced ETFs.
- You use one or two brokers and can tidy the export into its column layout.
- You have no options, share plans or complicated corporate actions, and any splits are easy to enter.
- You can find the ERI per share for your accumulation funds, or you do not hold any.
In that situation a free tool is a reasonable choice, and you may not need to pay for anything.
When FiscalFox is worth paying for
- US shares or other currencies: FiscalFox converts every trade at the rate for its own date, so you do not have to look up rates. See US shares and exchange rates.
- Several brokers with different file layouts: upload the original exports and FiscalFox combines the same holding across accounts. See the supported brokers.
- Many accumulation ETFs: published ERI is added for funds FiscalFox holds figures for, rather than typed in fund by fund. See the ERI guide.
- Corporate actions: spin-offs, mergers and share class changes as well as splits. See stock splits and corporate actions.
- RSUs and ESPP from Schwab or Morgan Stanley, options from supported brokers, and crypto from a Koinly report in the same calculation.
- Workings someone else will check: a report pack with every disposal and pool movement that an accountant can follow.
- A file that will not import: the done-for-you service prepares your report for £100 within 2 working days, with a full refund if it cannot be done or is late.
Using both as a check
You do not have to choose. Run your history through whatsmycgt and through the free FiscalFox calculation. If the gains agree, that is good evidence your data is complete. If they differ, look at the disposals that differ: a currency conversion, a missing file, a corporate action or ERI is the usual cause. Read the FiscalFox methodology to see how each rule is applied.
About this comparison
This comparison is not a claim that whatsmycgt is inaccurate. It sets out what each tool documents on its own website on the date checked. FiscalFox is independent and is not affiliated with, endorsed by or sponsored by whatsmycgt. The whatsmycgt name belongs to its owner. Neither tool gives tax advice; check unusual transactions with a qualified adviser.
Frequently asked questions
Is whatsmycgt really free?
Its website says it is free forever, with no sign-ups, subscriptions or hidden charges. FiscalFox's calculation preview is also free; the downloadable report pack costs £39.99 per tax year.
When is whatsmycgt enough?
When your trades are in pounds, you can put them in one spreadsheet with date, ticker, buy or sell, quantity, price and fee columns, and you are happy to enter any ERI and share splits yourself. It applies the same-day, 30-day and Section 104 rules and gives SA108 box figures, all in your browser.
What is the main difference from FiscalFox?
How the data gets in. whatsmycgt asks for a spreadsheet in a set column layout with every amount already in pounds, and you enter ERI and share splits yourself. FiscalFox reads the original exports from 18 brokers, converts foreign currency at the Bank of England daily rate, adds published ERI for funds it holds figures for, and researches corporate actions such as splits and spin-offs.
Which is more private?
whatsmycgt says everything runs in your browser and your trade data never leaves your device. FiscalFox reads its built-in broker files in your browser where possible, but saving your work needs an account and some features, such as the AI import and corporate action research, send data to AI providers. If keeping every row on your own device matters most, whatsmycgt is built around that.
Official UK tax references
This guide is checked against published GOV.UK and HMRC material. FiscalFox is a calculation tool, not personal tax advice; review unusual transactions with a qualified adviser.