How to Report Capital Gains Tax: Self Assessment or the Real-Time Service
Gains on shares, funds, crypto and other assets (anything except UK residential property) are reported in one of two ways: on your Self Assessment tax return, or through HMRC's real-time Capital Gains Tax service.1 For a gain made in 2026/27, the real-time service must be used by 31 December 2027, a Self Assessment return is due online by 31 January 2028, and the tax is due by 31 January 2028 either way. UK residential property with tax to pay has its own 60-day return.
- The real-time service is for UK residents reporting their own gains. It covers disposals in 2025/26 and 2026/27.1
- It cannot be used for UK residential property, for foreign tax credit relief on overseas property, or for life insurance gains.1
- You must attach your calculations to a real-time report. HMRC then sends a payment reference starting with X.1
- If you are in Self Assessment, HMRC's notes say to fill in the capital gains pages if you sold chargeable assets worth more than £50,000, your gains before losses were more than £3,000, or you want to claim a loss.2
- 2026/27 rates: 18% within your unused basic-rate band, 24% above it, after the £3,000 annual exempt amount.
Which route should you use?
| What you sold | How to report | Deadline |
|---|---|---|
| UK home that was not your main home, tax to pay | UK property return (60-day) | Report and pay within 60 days of completion |
| Shares, funds, crypto, other assets: you already file Self Assessment | Self Assessment (SA108 capital gains pages) | 31 January 2028 online |
| Shares, funds, crypto, other assets: not in Self Assessment | Real-time CGT service, or register for Self Assessment | Report by 31 December 2027; pay by 31 January 2028 |
| Overseas property | Self Assessment (the real-time service cannot give foreign tax credit relief) | 31 January 2028 online |
The paper Self Assessment deadline is 31 October 2027. If you are registered for Self Assessment, a sale reported through the real-time service or the 60-day return must also go on your tax return.1
For a property sale, follow our step-by-step guide to the 60-day return instead. For property abroad, see CGT on property sold abroad.
Do you have to report a gain at all?
If you are not in Self Assessment and your gains for the year, after costs, are within the £3,000 allowance, there is normally nothing to report. You do need to act if:
- your taxable gains are above the allowance, so there is tax to pay;
- you fill in a Self Assessment return and you sold chargeable assets worth more than £50,000 in the year, even with no tax due;2
- you made a loss you want to use later. A loss has to be claimed within 4 years of the end of the tax year: by 5 April 2031 for a 2026/27 loss. See CGT losses.
You never report shares held in an ISA or a pension, gilts, a private car, or your main home where Private Residence Relief covers the whole gain.2
How does the real-time CGT service work?
- Work out your gain for each disposal, using the matching rules for shares and crypto. The shares CGT calculator applies the same-day, 30-day and Section 104 pool rules.
- Sign in to the service from GOV.UK's "Report and pay your Capital Gains Tax" page.
- Enter the disposal and attach a copy of your calculation.
- Note your report reference, which starts with RTT. You need it to send a corrected report later.1
- Pay by 31 January after the tax year using the X payment reference HMRC sends you, by card online or bank transfer.3
The service suits a one-off gain: someone who sold a share portfolio or some crypto and has no other reason to file a tax return. If you have other untaxed income, such as rent or self-employment, Self Assessment is the right place for everything.
How do you report through Self Assessment?
Fill in the Capital Gains summary pages (SA108) with your return.2 Since 2024/25 the return has a separate section for cryptoassets: number of disposals, proceeds, costs and gains or losses. You enter totals for each type of asset and send your computations with the return. Do not deduct the £3,000 allowance yourself: HMRC applies it.
If you are not registered for Self Assessment and want to use it, register by 5 October after the end of the tax year (5 October 2027 for 2026/27).4 Our CGT reporting deadlines page lists every date.
Prefer to understand the rules before you fill anything in: matching, losses, reliefs and the key dates? get the CGT Survival Pack, £4.99 →
Worked example: a one-off share sale
Sam earns £60,000, does not file Self Assessment, and in September 2026 sells shares held outside an ISA for £38,000. His Section 104 pool cost for those shares is £24,000, including dealing fees. He has made no other gains.
| Sale proceeds | £38,000 |
| Less pooled cost | −£24,000 |
| Gain | £14,000 |
| Less annual exempt amount | −£3,000 |
| Taxable gain | £11,000 |
| CGT at 24% (no basic-rate band left) | £2,640 |
Sam can report through the real-time service at any point up to 31 December 2027, attaching this calculation, and pays £2,640 by 31 January 2028. If he made a further gain later in the tax year, he would send another report.
What if you made a mistake in a report?
For the real-time service, send a new report quoting your RTT reference. For Self Assessment, amend the return online within 12 months of the filing deadline. If you later find a cost you missed, the tax goes down; if you missed a disposal, tell HMRC promptly to keep penalties to a minimum.
Work out the figure to report
Enter your proceeds, costs, losses and income for an instant 2026/27 CGT figure.
Open the CGT calculatorFrequently asked questions
Can I report capital gains without filing a Self Assessment return?
Yes. If you are UK resident you can use HMRC's real-time Capital Gains Tax service for assets other than UK residential property. For a 2026/27 gain, report by 31 December 2027 and pay by 31 January 2028. If you are registered for Self Assessment, you must also include the sale on your return.
Do I have to report gains that are under the £3,000 allowance?
Usually not, unless you fill in a Self Assessment return and you sold chargeable assets worth more than £50,000, or you want to claim a loss. In those cases HMRC's notes say to complete the capital gains pages even if no tax is due.
What is the deadline for reporting capital gains for 2026/27?
Self Assessment: 31 January 2028 online (31 October 2027 on paper), with tax due by 31 January 2028. Real-time service: report by 31 December 2027 and pay by 31 January 2028. UK residential property with tax to pay: 60 days from completion.
Can I use the real-time service for crypto?
Yes. The service covers gains on assets such as shares, funds and cryptoassets for UK residents. It cannot be used for UK residential property, for foreign tax credit relief on overseas property, or for life insurance gains.
Do I have to attach my calculations?
Yes. GOV.UK says you must attach a copy of your calculations when you report a gain through the real-time service, and HMRC's Self Assessment notes ask for your computations with the capital gains pages.
This page is general information, not tax advice. It reflects GOV.UK guidance and HMRC's 2026 Capital Gains summary notes as checked on 18 October 2026.
Sources & references
The rates, allowances and rules in this guide are drawn from the official HMRC and GOV.UK sources below, checked for the 2026/27 tax year. Each link opens the relevant government page in a new tab.
- Report and pay CGT: if you have other capital gains to report www.gov.uk/report-and-pay-your-capital-gains-tax/if-you-have-other-capital-gains-to-report
- Self Assessment: Capital Gains summary (SA108) and notes www.gov.uk/government/publications/self-assessment-capital-gains-summary-sa108
- Report and pay CGT: ways to pay www.gov.uk/report-and-pay-your-capital-gains-tax/ways-to-pay
- Self Assessment tax returns www.gov.uk/self-assessment-tax-returns
- Report and pay CGT: if you sold a UK property on or after 6 April 2020 www.gov.uk/report-and-pay-your-capital-gains-tax/if-you-sold-a-property-in-the-uk-on-or-after-6-april-2020