Last updated: March 2026
This article is general information about UK tax rules, as we understand them on the date shown. It is not advice on your circumstances. Tax rules depend on your own facts and can change, so please speak to a tax professional before acting on it.
All capital losses should be reported, as it is the only way they can be ‘claimed’ to use against future gains. Losses can be reported to HMRC on the Tax Return or by letter.
The time limit for claiming capital losses is within 4 years of the end of the tax year in which the capital loss was realised.
💡 HINT: Don't confuse the end of the tax year (5th April) with the tax deadline (31st January). Many do and lose the opportunity to claim the loss!
If you don’t already file a Tax Return, you need to notify HMRC that you have capital gains or losses to report by 5th October after the end of the tax year. You can do this by registering for self assessment, they will then issue you with a Notice to File a Tax Return. You need to submit the Tax Return to HMRC by 31st January after the end of the tax year to avoid late filing penalties.
A tax year runs from 6th April to 5th April. If you made a disposal on 4th April 2026 (or started to receive income in the year ended 5th April 2026), this falls in the 2025/26 tax year (ending 5th April 2026) and you need to register with HMRC by 5th October 2026 and submit the tax return by 31st January 2027.
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