How to report crypto to HMRC: Self Assessment, the real-time service, deadlines and penalties

Telling HMRC about crypto is no longer something you can leave vague. Since the 2024 to 2025 tax year, the Self Assessment return has a dedicated cryptoasset section, and from 2027 HMRC will receive information about users directly from crypto platforms. This guide explains when you need to report, the two ways to do it, the deadlines and what happens if you miss them.

For how gains are calculated in the first place (pooling, the same-day and 30-day rules, rates), see UK crypto tax.

Do you need to report?

HMRC says you may need to pay Capital Gains Tax when you dispose of cryptoassets by:

• selling them,
• exchanging them for a different cryptoasset,
• using them to pay for goods or services,
• giving them to someone else (unless it’s a gift to your spouse, civil partner or a charity).

You then add up your gains for the tax year, which runs from 6 April to 5 April, and deduct allowable losses. GOV.UK sets out three situations:

Remember that every swap counts. Exchanging one cryptoasset for another is a disposal, so proceeds can add up quickly even if you never cashed out to pounds.

Option 1: the Self Assessment return

You can report your gains on a Self Assessment return in the tax year after you made them. According to HMRC:

• Complete the return in pounds sterling.
• Use the cryptoasset section, available on returns for the 2024 to 2025 tax year onwards.
• HMRC then tells you how much you owe and when to pay.

If you’ve never filed a return before, or you didn’t need to file for the previous year, you must tell HMRC by 5 October that you need to complete one, by registering for Self Assessment.

What goes in the cryptoasset boxes

The cryptoasset section is on the Capital Gains Tax summary pages (SA108), in boxes 13.1 to 13.8. HMRC’s notes for the 2025 to 2026 return explain each one:

Because every swap is a disposal, the number of disposals in box 13.1 can be large even for a modest investor. Your own records of each pool are what make these totals possible.

Option 2: the real-time Capital Gains Tax service

If you’re a UK resident, you can instead report gains on assets sold during the 2025 to 2026 and 2026 to 2027 tax years using HMRC’s real-time service. GOV.UK says:

• You must attach a copy of your calculations.
• You must report by 31 December in the tax year after you made the gain, and pay by 31 January. For a gain in the 2025 to 2026 tax year: report by 31 December 2026, pay by 31 January 2027.
• HMRC sends a payment reference starting with “X”.
• If you’re already registered for Self Assessment, you must also include the gains in your return.

The real-time service is useful if you don’t otherwise need a Self Assessment return and only have gains to report.

Key deadlines

For the tax year that ended on 5 April 2026:

Payments on account don’t include Capital Gains Tax

Unless last year’s Self Assessment bill was under £1,000, or more than 80% of your tax was already collected at source, GOV.UK says you have to make payments on account towards the next year, each half of last year’s tax, by 31 January and 31 July. HMRC’s manual says Capital Gains Tax is excluded from that calculation. Any Capital Gains Tax you owe is simply paid as part of the balancing payment by 31 January after the tax year. So a big crypto gain one year doesn’t, on its own, raise your advance payments for the next.

Penalties if you’re late

GOV.UK lists the Self Assessment penalties:

• Late return: an initial £100; after 3 months, £10 a day up to £900; after 6 months, a further 5% of the tax due or £300, whichever is greater; and the same again after 12 months.
• Late payment: 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest. HMRC’s late payment interest rate is the Bank of England base rate plus 4%, which has been 7.75% since 9 January 2026. See how to disclose unpaid crypto tax.
• Registering late: if you register after 5 October and don’t pay all your tax by 31 January, you may get a failure to notify penalty.

A worked example from GOV.UK

GOV.UK’s own example for gains made on or after 6 April 2026 works the same way for crypto. Suppose your taxable income (after your Personal Allowance) is £20,000 and your taxable gains are £12,600:

1. Deduct the £3,000 allowance: £12,600 − £3,000 = £9,600.
2. Add it to your taxable income: £20,000 + £9,600 = £29,600, which is below the £37,700 basic rate band for 2026 to 2027.
3. So the whole £9,600 is taxed at 18%: £1,728.

Gains that fall above the basic rate band are taxed at 24%.

Income from crypto goes elsewhere

Not everything you get from crypto is a capital gain. HMRC treats tokens received from staking, lending or mining, and in some cases airdrops, as income, usually miscellaneous income if you’re not trading. Those go in the income parts of your return. See staking taxes, crypto airdrops and getting paid in crypto.

Records to keep

HMRC says it will ask to see your records if it carries out a compliance check. For each pool of tokens, keep for every transaction:

• the type of token and the date you disposed of it,
• the number of tokens disposed of and the number you have left,
• the value in pounds at the time,
• bank statements,
• your pooled costs before and after the disposal.

HMRC also warns that the reports exchanges provide aren’t tax calculations and don’t track your pooled costs. Keep your own records.

Missed something in earlier years?

If you didn’t report crypto gains or income in past years, HMRC has a separate Cryptoasset Disclosure Service, and it will start receiving data from crypto platforms in 2027. See the CARF and new exchange reporting.