Deadlines for loss claims

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Two kinds of time limit

The general rule. Section 43(1) of the Taxes Management Act 1970 says no claim for income tax or Capital Gains Tax relief may be made more than 4 years after the end of the tax year it relates to, unless another law sets a longer or shorter period. HMRC’s claims manual gives the example that a claim for 2008-09 had to be made by 5 April 2013.

Shorter limits for relief against income. Several loss reliefs set their own, shorter limit: the first anniversary of the normal Self Assessment filing date — that is, 12 months after the 31 January following the tax year.

The main limits for a 2026/27 loss

The claim deadline calculator works these out for any tax year and shows how many days are left.

Self Assessment dates (2025/26 return, due in 2026/27)

GOV.UK gives these deadlines for the return for the tax year that ended on 5 April 2026:

• 5 October 2026 — tell HMRC if you need to file and haven’t before (or didn’t need to for 2024 to 2025);
• 31 October 2026 — paper returns (by 11:59pm);
• 30 December 2026 — online, if you want the bill collected through your tax code;
• 31 January 2027 — online returns, and paying the tax you owe (balancing payment and any first payment on account);
• 31 July 2027 — second payment on account, if you make them.

Late filing penalties start at £100, with more after 3, 6 and 12 months; late payment penalties are 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest. GOV.UK explains that you can appeal if you have a reasonable excuse.

If you register late, GOV.UK says HMRC will give you a filing deadline 3 months from its letter, but the tax must still be paid by 31 January.

Capital gains reported outside Self Assessment

If you use GOV.UK’s "real time" Capital Gains Tax service (UK residents, not for UK residential property), you must report by 31 December after the tax year and pay by 31 January. A UK residential property gain with tax to pay must be reported and paid within 60 days of completion — see property disposal losses.

Companies

A company’s claim to set a trading loss against profits of the same period or the previous 12 months must be made within 2 years after the end of the loss-making accounting period, or a longer period if HMRC allows (Corporation Tax Act 2010 s37). See company trading losses.

Sources

Checked 4 October 2026 for the 2026/27 tax year. We read these primary sources for this guide:

1. Taxes Management Act 1970, section 43 (legislation.gov.uk)
2. HMRC Self Assessment Claims Manual SACM3035: Time limits (gov.uk)
3. GOV.UK: Self Assessment tax returns — Deadlines (gov.uk)
4. GOV.UK: Check how to register for Self Assessment (gov.uk)
5. GOV.UK: Self Assessment tax returns — Penalties (gov.uk)
6. GOV.UK: Capital Gains Tax — If you make a loss (gov.uk)
7. HMRC Business Income Manual BIM85075: Time limits for trade loss claims (gov.uk)
8. Income Tax Act 2007, section 64 (legislation.gov.uk)
9. Income Tax Act 2007, section 132 (legislation.gov.uk)
10. Income Tax Act 2007, section 124 (legislation.gov.uk)
11. Taxation of Chargeable Gains Act 1992, section 24 (legislation.gov.uk)
12. Corporation Tax Act 2010, section 37 (legislation.gov.uk)
13. GOV.UK: Report and pay your Capital Gains Tax (gov.uk)

Contains public sector information licensed under the Open Government Licence v3.0. This guide adapts and summarises that information in our own words. taxloss.co.uk is an independent guide. It is not affiliated with, endorsed by or connected to HM Revenue & Customs (HMRC) or the UK Government. Spotted something out of date? Tell us.

More on returns, deadlines & records

• 20Where losses go on your Self Assessment returnA plain-English map of the loss boxes on the Self Assessment supplementary pages — capital gains (SA108), self-employment (SA103), partnership (SA104), UK property (SA105) and additional information (SA101). Box numbers are from the 2025–26 forms.
• 21Amending a return or claiming laterForgot to claim a loss? You can usually amend your Self Assessment return within 12 months of the 31 January deadline. After that, many loss claims can still be made by letter within their own time limits — and overpayment relief is available for up to 4 years.
• 22Making Tax Digital for Income Tax from April 2026Since 6 April 2026, sole traders and landlords with qualifying income over £50,000 must keep digital records, send quarterly updates and file their tax return through compatible software. Here’s who is affected, when, and what GOV.UK says about losses.
• 23Records and evidence HMRC may ask forTo claim a loss you need to be able to show how you worked it out. What to keep for capital losses, crypto and business losses, how long to keep it, and what HMRC can ask for in a compliance check.
• 24When to get professional helpMany losses are simple enough to claim yourself. Some aren’t — large or complex losses, businesses stopping, partnerships and companies, overseas issues or an HMRC check. Here’s who can help, and how to choose.