This tool currently supports the following brokers:
For Trading 212 and Vanguard, only General Investment Account (GIA) transactions are relevant for Capital Gains Tax. ISA transactions are tax-free and excluded from calculations.
If your broker is not listed above, you can prepare a simple text file in CGTCalculator format (see below) to import your trades.
Interactive Brokers (IBKR):
Charles Schwab:
Trading 212:
Make sure you export from your Invest or GIA account, not your ISA account.
Vanguard UK:
CGTCalculator format (any broker):
If your broker isn't directly supported, you can create a simple text or CSV file with one trade per line in the following format:
B 06/04/2024 AAPL 100 150.00 10.00 S 15/04/2024 AAPL 50 160.00 8.50
Fields (whitespace-separated):
All prices must be in GBP. Save the file as .csv or .txt and upload it like any other activity file. This format is compatible with cgtcalculator.com.
Important: Capital Gains Tax calculations need your full transaction history to accurately compute cost basis, and transactions up to 30 days after the tax year end for bed & breakfast matching. We recommend exporting from when you first opened your account to at least 5 May (30 days after 5 April). Interest and dividend reports only require the current tax year's data.
Yes, you can upload multiple files at once. This is useful when:
The tool will automatically detect each file's format and combine all transactions for a unified tax calculation. All files should cover the same tax year for accurate results.
The UK tax year runs from 6 April to 5 April the following year. For example:
Enter the tax year in the format shown (e.g., "2024-25"). Your exported files should include all transactions from when you first opened your account up to 30 days after 5 April. The tool uses historical transactions to calculate cost basis and the 30-day window after the tax year for bed & breakfast matching.
No. Transactions within an Individual Savings Account (ISA) are completely tax-free under UK law. You do not need to report ISA gains, losses, dividends, or interest to HMRC.
This tool is designed for General Investment Accounts (GIA) and other taxable accounts only. If you upload a file containing ISA transactions, they will be excluded from the calculations.
Yes. The output is structured to match the HMRC Self Assessment forms:
Each box is labelled with its HMRC reference number. You can use the "Copy" button next to each value to copy it directly and paste into your online Self Assessment form or paper return.
On 30 October 2024, the UK Government changed Capital Gains Tax rates with immediate effect:
Because the rates changed mid-year, your gains need to be split into two periods. HMRC's Self Assessment system does not automatically calculate the correct tax, so you must:
This tool automatically splits your gains into pre- and post-30 October periods to help you with this calculation.
HMRC has specific rules for calculating Capital Gains Tax that may differ from how your broker reports performance. Key differences include:
This tool applies HMRC's rules, which is why results may differ from your broker's dashboard.
Tax loss harvesting is the practice of selling investments at a loss to offset capital gains and reduce your tax bill. Under HMRC rules, capital losses can be set against gains in the same tax year. The Tax Loss Harvesting tab analyses your current holdings and identifies securities trading below your cost basis that you could sell to offset your realized gains.
Under HMRC's "Bed and Breakfast" rule, if you sell a security at a loss and repurchase the same security within 30 days, the loss is not allowable — instead, the new purchase is matched with the sale. To ensure your harvested loss counts, you must wait at least 30 days before repurchasing. The "Safe to Repurchase" date shown in the suggestions accounts for this rule.
The tool uses the previous trading day's closing prices to estimate unrealized gains and losses. Actual proceeds will depend on the price at which you execute the trade, which may differ due to market movements and bid-ask spread. Dealing costs (commissions, stamp duty) are not included. Use the estimates as a guide for decision-making, not as exact figures.
No. This tool is provided for informational purposes only and does not constitute tax, legal, or financial advice.
While we strive for accuracy, tax rules are complex and individual circumstances vary. You are responsible for ensuring your Self Assessment is correct and complete.
If you are unsure about your tax obligations, please consult a qualified tax adviser or accountant, or contact HMRC directly.
No. Your files are processed entirely in memory and are not stored on any server. Once your calculation is complete and the results are displayed, the uploaded data is discarded.
No account registration is required, and no personal or financial data is retained. Your transaction history remains private.
If something doesn't look right, here are common causes and solutions:
If you believe there's an issue with the tool itself, please re-export your data to ensure you have the latest version, or contact support with details of the problem.