Report a Crypto Gain Without Self Assessment: HMRC's Real Time Capital Gains Tax Service

Most guides tell you that a crypto gain above the annual exempt amount means registering for Self Assessment. That is one route. For a PAYE employee with no other reason to file a return, there is a lighter one: HMRC's real time Capital Gains Tax service, which lets you report a gain and pay the tax online without ever completing SA100 or SA108.

Who can use it

The service is for individuals who are UK resident, have a chargeable gain to report, and are not registered for Self Assessment for the year. If you already file a return — because you are self-employed, a landlord, a higher earner with untaxed income, or for any other reason — you cannot use it. Your crypto gains go on the SA108 pages of the return you are already filing.

It also cannot be used for UK residential property disposals, which have their own 60-day service, and it is not for trusts or companies.

The practical profile: employed, taxed under PAYE, holds crypto as an investment, sold some during the year at a gain above £3,000, and would rather not register for Self Assessment just to report one figure. That describes a large share of UK crypto holders.

When you have to report at all

You must report and pay if your total net gains in the tax year exceed the annual exempt amount — £3,000 for 2025/26 and 2026/27 under TCGA 1992 s.1K.

If you are already in Self Assessment there is a second trigger: total disposal proceeds above £50,000 in the year, even if the gain is under the exemption. That rule applies to people completing a return; it does not by itself force someone outside Self Assessment to register. Losses do not have to be reported unless you want to claim them — and you should, because an unclaimed loss cannot be carried forward (s.16(2A)).

Deadlines

The 31 December reporting deadline is earlier than the Self Assessment online filing deadline of 31 January. Payment is still due by 31 January. After you submit, HMRC issues a payment reference and you pay by bank transfer, card or through your online account.

If you miss 31 December you are back in the Self Assessment world: you should notify HMRC of chargeability by 5 October following the tax year under TMA 1970 s.7 and file a return. The full deadlines guide has every date.

What you need before you start

The service asks for the figures, not the workings, but it also asks you to keep the workings in case HMRC wants them. You will enter:

• Total disposal proceeds in the year.
• Total allowable costs, including incidental costs of acquisition and disposal (TCGA 1992 s.38).
• Total gains before losses, and losses in the year.
• Any losses brought forward from earlier years that you are using.
• Your income for the year, so HMRC can apply the 18% and 24% rates correctly (s.1H, s.1I).
• The tax due, which the service calculates once the above is in.

You can attach a PDF computation. Doing so is sensible: a per-disposal schedule in the HS284 format — date, asset, proceeds, cost, matching rule, gain — is exactly what an officer would ask for and pre-empts the question.

Worked example

Employed, salary £42,000. During 2025/26 sold Bitcoin in three tranches: total proceeds £19,500, allowable cost £11,200 including fees, no losses, nothing brought forward. Not registered for Self Assessment.

• Net gain: £19,500 − £11,200 = £8,300
• Less annual exempt amount: £3,000
• Taxable gain: £5,300
• Income after personal allowance: £42,000 − £12,570 = £29,430
• Unused basic rate band: £37,700 − £29,430 = £8,270
• The whole £5,300 fits in the basic rate band, so CGT at 18%: £954

Report through the service by 31 December 2026, pay £954 by 31 January 2027, keep the three-line computation. No SA100, no SA108, no registration. If the same person had also received £700 of staking rewards, they would have miscellaneous income to report — that cannot go through the CGT service and would normally mean a return, or at least a call to HMRC to have it coded out.

Step by step

1. Prepare the computation first: proceeds, allowable costs, gains and losses per disposal, and the totals. Do not start the online form until you have the figures — it does not save a half-finished report reliably.
2. Sign in to your Government Gateway account, or create one. You will need your National Insurance number and a way to verify your identity.
3. From the personal tax account, go to the Capital Gains Tax section and choose to report a gain using the real time service.
4. Enter the tax year, the asset type (other assets — cryptoassets are not shares or property), the totals, and your estimated income for the year.
5. Attach your computation as a PDF if you have one.
6. Submit. HMRC issues a reference number and, within a few weeks, a confirmation of the tax due with payment instructions.
7. Pay by 31 January. Late payment interest runs from that date regardless of when HMRC's confirmation arrived.

Keep the submission reference. It is your evidence that the gain was reported on time if a question is ever raised.

If you also made a loss

The service handles losses in the same year: enter total gains and total losses and it nets them. It also lets you use losses brought forward from earlier years, provided those losses were claimed within four years of the year they arose (TCGA 1992 s.16(2A)). What it does not do well is establish a new loss to carry forward when there is no gain to report this year. If 2025/26 was a net loss year, the cleanest route is a return with the loss claimed on SA108, or a letter to HMRC making the claim; otherwise the loss can lapse unclaimed. The crypto losses guide covers the claim mechanics.

When you should register for Self Assessment instead

• You have any crypto income. Staking, airdrops, mining — the real time service is capital gains only.
• You will be doing this every year. Repeated one-off reports are more effort than a return.
• Losses to carry forward. The service lets you use brought-forward losses but a return is the cleaner place to establish and track them.
• Proceeds over £50,000 and you want the reporting on record, or an accountant is involved, or there is anything unusual — a swap-heavy year, a negligible value claim under s.24, a spousal transfer under s.58.
• HMRC has already asked you to file.

Keep the computation

Whether you use the service or a return, the legal obligation is the same: an accurate figure, with records to support it. HMRC's Cryptoassets Manual at CRYPTO10400 lists what it expects you to keep — type of token, dates, quantities, sterling values, wallet addresses, pooled costs. A calculator that produces the per-disposal schedule and the closing pool per token gives you the attachment and the record in one go; cryptolens.uk's free tier does that for a single wallet if you want to see the shape before deciding which route to use.

This is general information, not personal tax advice.