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Self Assessment filing for UK cryptoasset holders.

If you disposed of cryptoassets, received staking or mining rewards, or held DeFi positions in a tax year, Self Assessment is almost certainly required. The SA108 capital gains supplementary pages carry dedicated cryptoasset entries. Two points catch holders by surprise: gains must be reported even when no tax is due once disposal proceeds exceed the reporting threshold, and <a href="https://www.gov.uk/guidance/check-if-you-need-to-pay-tax-when-you-sell-cryptoassets">every crypto-to-crypto swap is a disposal</a> at sterling market value, not just withdrawals to a bank account. The firm handles the full Self Assessment: reconstruct disposals under <a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto22200">s104 pooling</a>, compute gains and income-side receipts, complete the SA108 entries, and submit before the 31 January deadline.

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5 Oct
Self Assessment registration deadline following the tax year in which first reportable gains or income arose
31 Jan
Online Self Assessment filing and payment deadline
SA108
Dedicated cryptoasset entries on the capital gains supplementary pages

The challenges clients face.

Reporting is required even when no tax is due

Where disposal proceeds exceed the reporting threshold, the disposals must be reported inside Self Assessment even if the <a href="https://www.gov.uk/capital-gains-tax/allowances">£3,000 annual exempt amount</a> covers the gain and no tax is payable. This is the single most common DIY miss: a nil-tax position is not a nil-reporting position. Failure to report when required carries late-filing penalties and may prompt an enquiry.

Every swap is a disposal, whether or not you saw sterling

Exchanging one token for another is a <a href="https://www.gov.uk/guidance/check-if-you-need-to-pay-tax-when-you-sell-cryptoassets">taxable disposal at the sterling market value</a> at the time of the swap. An active holder who never converted to fiat may have hundreds of reportable disposals. Spending crypto on goods or services and gifting crypto (except to a spouse or civil partner) are also disposals. The filing obligation follows the disposals, not the bank statements.

S104 pooling, not FIFO, determines your allowable cost

<a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto22200">Section 104 pooling</a> holds each token at average cost across all acquisitions. Software that defaults to FIFO or specific identification produces an incorrect UK figure. The <a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto22250">same-day and 30-day matching rules</a> then override the pool. An SA108 submission built on the wrong method is not a defensible filing.

Staking and mining income needs its own treatment before the CGT question arises

Staking and mining rewards are taxable on receipt at sterling value as miscellaneous or trading income. That receipt value also becomes the <a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto21200">CGT base cost</a> for the later disposal. The two-step means both the income side and the gains side of the SA return need separate treatment, not a single CGT entry.

How we help.

Complete disposal reconstruction under the correct UK method

We gather every exchange export and on-chain record, compute disposals under <a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto22200">s104 pooling</a> at average cost, apply same-day and 30-day matching, and reconcile the total gains and losses. The result is a set of figures ready to carry onto the SA108 capital gains pages, with each disposal defensible if HMRC asks.

Income-side treatment for staking, mining, airdrops and DeFi receipts

We classify each token receipt against its income character: miscellaneous income, trading income, or a capital acquisition with no income at point of receipt (such as an unsolicited airdrop). Each category feeds the correct SA box. Where DeFi treatment is uncertain under <a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto61000">HMRC's current analysis</a>, we present the position honestly rather than applying a blanket rule.

SA108 completion and submission before the 31 January deadline

We complete the SA108 cryptoasset entries and the wider Self Assessment return, review for consistency, and submit electronically by the 31 January deadline. If <a href="https://www.gov.uk/register-for-self-assessment">registration by 5 October</a> has been missed for an earlier year, we advise on late registration and, where prior years are affected, on whether a voluntary disclosure through the <a href="/services/hmrc-disclosure">cryptoasset disclosure service</a> is the better route.

Common questions

Do I need to do a Self Assessment for crypto?
Yes, if you disposed of cryptoassets in the tax year (including swaps and spending), received staking or mining income, or if your disposal proceeds exceed the CGT reporting threshold. <a href="https://www.gov.uk/self-assessment-tax-returns/who-must-send-a-tax-return">HMRC's registration guidance</a> sets out the full triggers. The filing obligation follows the disposals, not whether tax is actually owed.
What is the 5 October deadline?
If it is your first year needing Self Assessment, you must <a href="https://www.gov.uk/register-for-self-assessment">register with HMRC by 5 October</a> following the end of the tax year in which the first reportable gains or income arose. Missing that date does not remove the obligation; it adds a potential late-registration issue on top.
Do I have to report crypto if I made no profit or stayed under the annual exempt amount?
Possibly yes. Where your disposal proceeds exceed the reporting threshold, you must report the disposals inside Self Assessment <a href="https://www.gov.uk/capital-gains-tax/reporting-and-paying-capital-gains-tax">even if no tax is due</a> because the <a href="https://www.gov.uk/capital-gains-tax/allowances">£3,000 annual exempt amount</a> covers the gain. The reporting obligation and the tax liability are separate questions.
I only swapped one coin for another. Do I report that?
Yes. A swap is a <a href="https://www.gov.uk/guidance/check-if-you-need-to-pay-tax-when-you-sell-cryptoassets">disposal at sterling market value</a> at the moment of the exchange. Every token-for-token trade is a reportable event. The most common misconception is that only withdrawals to a bank account create a tax event.
I received staking rewards. Where do those go on my tax return?
Staking rewards are typically taxable as <a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto21200">miscellaneous income on receipt</a>, valued in sterling at that point. That receipt value also becomes your CGT base cost for the later disposal of those tokens. The two-step means both an income entry and a future CGT entry, not just one or the other.
What if I should have filed in previous years?
If you have unreported crypto gains or income from earlier years, a voluntary disclosure through <a href="/services/hmrc-disclosure">HMRC's cryptoasset disclosure service</a> is the right route, not late Self Assessment returns alone. The number of years covered and the penalty outcome depend on your behaviour band. Come forward before HMRC contacts you to secure the lowest available penalty range.
Can I just use my Koinly report to file?
A Koinly or Recap report is a useful starting point, but it needs review before it goes on the SA108. UK individuals must use <a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto22200">s104 pooling at average cost</a>, not FIFO or specific identification. The same-day and 30-day matching rules are also beyond most stateless tools. We offer a <a href="/services/koinly-recap-reconciliation">dedicated reconciliation service</a> that verifies the method and flags any misclassifications before we file.
What is the annual exempt amount for 2026/27?
The <a href="https://www.gov.uk/capital-gains-tax/allowances">CGT annual exempt amount is £3,000</a> for 2026/27. It is not a filing exemption: if your disposal proceeds exceed the reporting threshold you must report the disposals even if the exempt amount covers the gain. The allowance is also per person, not per asset, so active traders with many disposals often exhaust it in the first transaction or two once swaps are counted.

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