How to claim a capital loss — and the 4-year time limit

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Why you have to claim

Section 16(2A) of the Taxation of Chargeable Gains Act 1992 says a loss is not an allowable loss unless you give HMRC a notice that quantifies it — states the amount. The same subsection makes that notice work like a claim for relief, so the normal rules for claims (including the time limit) apply.

HMRC’s Capital Gains Manual adds two practical points:

• there is no special claim form — including details of the loss in your tax return, with your computation of gains and losses, is the usual way of giving notice;
• once a loss is established, using it against later gains doesn’t need another claim.

So the claim is about putting the loss on record. You can — and usually should — claim a loss even in a year when you have no gains to use it against, so that it is available to carry forward.

The deadline

The general time limit for income tax and Capital Gains Tax claims is in section 43 of the Taxes Management Act 1970: no later than 4 years after the end of the tax year the claim relates to. For a capital loss, that is the tax year in which you disposed of the asset. GOV.UK puts it this way: you can claim up to 4 years after the end of the tax year that you disposed of the asset.

Our claim deadline calculator works these out for any year.

Claiming on your Self Assessment return

If you fill in a Self Assessment return, the loss goes on the Capital Gains Tax summary pages (form SA108, or the equivalent section online). HMRC’s notes say you need to fill in those pages if, among other things, you want to claim an allowable capital loss for the year — even if you had no gains.

In outline (box numbers from the 2025–26 edition — they can change from year to year):

• each section of the form — residential property, cryptoassets, other property and assets, listed shares, unlisted shares — has a "Losses in the year" box for losses on that type of asset;
• a "Losses and adjustments" section records losses brought forward and used, and the total available to carry forward;
• if the loss comes from a negligible value claim, there is a code to show that (see negligible value claims).

Attach or keep your computations. Our guide to where losses go on your return describes the pages in more detail.

Claiming by letter

GOV.UK says that if you’ve never made a gain and aren’t registered for Self Assessment, you can write to HMRC instead of filing a return. The law asks for a notice quantifying the loss, so it makes sense for your letter to include:

• your name, address and National Insurance number;
• what the asset was, and the dates you acquired and disposed of it;
• the amount you received (or the market value, if that applies) and your allowable costs;
• your calculation of the loss, and the tax year it arose in.

Keep a copy and proof of posting. If you’ve already made gains above the annual exempt amount, or sold assets for more than £50,000 in total, you may need to report through Self Assessment instead — check GOV.UK’s rules on reporting.

What happens next

Once claimed, the loss is set against your gains of the same tax year, and anything left is carried forward to later years. Read how capital losses are set against gains for the order, and why losses brought forward don’t waste your annual exempt amount.

Questions people ask

Do I have to report a capital loss to HMRC?

There’s no penalty for not reporting a loss — but a loss you don’t report can’t be used. The law says a capital loss is only an allowable loss once you have given HMRC notice of it, with the amount, within 4 years of the end of the tax year.

Report it in the capital gains pages of your tax return, or by letter if you’re not in Self Assessment and have never made a gain.

How long do I have to claim a capital loss?

Up to 4 years after the end of the tax year in which you disposed of the asset. A loss made in 2026/27 (the tax year ending 5 April 2027) must be claimed by 5 April 2031. The deadline calculator gives the date for any year.

Sources

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

1. GOV.UK: Capital Gains Tax — If you make a loss (gov.uk)
2. HMRC Capital Gains Manual CG15800: Losses — allowable losses (gov.uk)
3. HMRC Capital Gains Manual CG21500: Individuals — losses (gov.uk)
4. Taxation of Chargeable Gains Act 1992, section 16 (legislation.gov.uk)
5. Taxes Management Act 1970, section 43 (time limit for claims) (legislation.gov.uk)
6. HMRC: Self Assessment Capital Gains Tax summary (SA108) and notes (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 capital gains losses

• 01Capital losses: what counts as an allowable lossWhen you sell or give away an asset for less than it cost you, you may have a capital loss. It only reduces your tax once it is an "allowable loss" — which depends on the asset and on telling HMRC in time.
• 03How capital losses are set against gains — and the annual exempt amountThis year’s losses are used up in full first, even if that wastes your tax-free allowance. Losses brought forward from earlier years are only used to bring your gains down to the annual exempt amount — the rest carries on.
• 04Losses on disposals to family and connected peopleSell or give something to a relative, business partner or a company you control and make a loss, and that loss is "clogged" — you can only use it against gains on other disposals to the same person. Transfers to a spouse or civil partner usually give no loss at all.
• 05Shares that have become worthless: negligible value claimsIf shares (or other assets) you still own have become worth next to nothing, a negligible value claim lets you be treated as having sold them, creating a capital loss. The claim can be backdated — within limits.
• 06Share loss relief: setting a loss on shares against incomeLosses on shares you subscribed for in a qualifying unlisted trading company — including EIS and SEIS shares — can sometimes be set against your income instead of only against gains. The claim has a shorter deadline.
• 07Cryptoasset lossesSelling, swapping or spending tokens for less than their cost gives a capital loss you can claim like any other. HMRC treats lost keys and theft differently — and worthless tokens need a negligible value claim on the whole pool.
• 08Losses when you sell property — and the 60-day UK property returnA loss on selling a second home, buy-to-let or land is a capital loss you claim in the usual way. UK residents normally only use the 60-day "Capital Gains Tax on UK property" service when tax is due — non-residents must report every disposal, even a loss.