capital gains calculator
capital gains calculator

Welcome to CGTCalculator - keep track of your capital gain

Anyone who has tried working through the Inland Revenue matching rules for share trades will know that the process can quickly become very complicated for even a modest number of trades. The 30 day rule especially can cause unexpected gains/losses. The purpose of this site is to help UK tax payers to calculate, and to keep track of, their capital gain (or loss) based on their share trades. This is important for effective tax planning and can potentially save you a significant amount on your tax bill.

To use the capital gains calculator simply store your trades in a spreadsheet, or a simple text editor like Notepad, in a simple format. If you use an online stockbroker then check the conversion utilities for a suitable converter. Also note that transfers to spouse are supported. See the FAQ for frequently asked questions.

To view a bar chart showing the breakdown per stock of gains/losses over a tax year click the View Chart button.

This calculator is updated every year and is fully up to date for all tax years up to 2025-2026.

Capital Gains Info:
2024-2025 2025-2026
Exemption 3000 3000
Basic Rate 10 or 18% 18%
Higher Rate 20 or 24% 24%

Note for tax year 24/25 after 29/10/24 use the higher rate

Last updated July 2025