cgtcalc: UK capital gains tax calculator

Run a capital gains calculation from your transaction input, then inspect a drill-down of the matching and gain/loss math.

Disclaimer: I am not a financial professional and cannot give tax advice. This calculator is intended for sample purposes only. Always do your own calculations for your self assessment. I accept no responsibility for any errors this calculator produces.

  • This uses the cgtcalc Swift project to perform calculations. You can also run that project directly.
  • No data entered into this website is logged or stored on the server.

For supported input rows and exact field formats, use the cgtcalc input format documentation. Input parsing is strict (for example, exact field counts and zero-padded YYYY-MM-DD dates).

Input

Output

Interactive Report

Tax Year Summary

Showing all tax years
Tax Year Disposals Proceeds Total Gain Total Loss Net Gain/Loss Loss Carry Taxable Gain

Disposal Explorer

Date Tax Year Asset Proceeds Gain/Loss Matches

Calculation Drill In

Select a disposal row to view a detailed cost breakdown.

Holdings

Asset Quantity Cost Basis Average Cost

Sell Preview

Select a holding row to open the calculator.
The preview uses the real calculator with a hypothetical extra SELL row, so the gain/loss reflects the same matching rules as the main report.

Spouse Transfers Out

Date Asset Quantity Transferred Cost Basis Average Cost