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Crypto Tax UK: HMRC §104 Pool Guide

How HMRC taxes crypto in the UK: the Section 104 pool, same-day and 30-day bed-and-breakfasting rules, the CGT annual exempt amount, income tax on staking and mining, and SA108 filing. Coinfig reports for the UK in pounds sterling.

Last reviewed: · Reviewed by Johan Pretorius, Registered Tax Practitioner

Overview

In the United Kingdom, HM Revenue & Customs (HMRC) treats crypto assets (which it calls "cryptoassets") as property, not currency. For most individuals, gains on disposal fall under Capital Gains Tax (CGT), while certain receipts (mining, staking, airdrops in some cases, employment income in crypto) are subject to Income Tax. HMRC's Cryptoassets Manual sets out the detail.

Coinfig is live for the UK. Choose the United Kingdom as your country and Coinfig reports in pounds sterling, applying the Section 104 pool and the same-day and 30-day rules described below. You can subscribe and pay in pounds by card. See pricing for the plans and what each one includes. This guide is general information, not tax advice. Rules and allowances change each tax year, so confirm the current position with HMRC or an adviser.

Capital Gains Tax and the §104 pool

The defining UK feature is share-pooling, applied to crypto. For each token, HMRC requires you to maintain a Section 104 pool: a running aggregate of the quantity held and the pooled allowable cost. When you acquire more of the same token, both the quantity and the pooled cost increase; when you dispose, you deduct an average cost proportionate to the units sold. This is materially different from South Africa's FIFO/specific-ID approach.

Same-day and 30-day (bed-and-breakfasting) rules

Two matching rules override the pool and must be applied before the §104 pool:

  • Same-day rule: disposals are first matched with acquisitions of the same token made on the same day.
  • 30-day rule (the "bed-and-breakfasting" rule): next, disposals are matched with acquisitions in the following 30 days. This stops investors from selling to crystallise a loss and immediately rebuying at the same cost.

Only after applying the same-day and 30-day rules do you draw the remaining matched units from the §104 pool.

Allowance and rates

Each tax year individuals have a CGT annual exempt amount (which has been reduced in recent years, so confirm the current figure). Gains above the allowance are taxed at the CGT rates applicable to the year and your income band. Losses can be offset and carried forward if claimed.

Income Tax on crypto

Crypto received as employment income, from mining or staking carried out as taxable activity, or as certain airdrops (especially where received in return for something), is subject to Income Tax (and possibly National Insurance), valued in pounds at receipt. That value becomes the acquisition cost for a later CGT disposal.

Filing: Self Assessment and SA108

Report capital gains on the SA108 Capital Gains Summary supplementary pages of the Self Assessment return (and the crypto-specific entries HMRC requires). Income from crypto goes in the relevant income sections. Keep records of every acquisition and disposal, the pooled cost, and the pound values used.

Last reviewed

UK allowances and rates change each tax year. Confirm the current annual exempt amount and CGT rates with HMRC before filing. This is general information, not tax advice.

Tax treatment at a glance

TransactionEventTreatment
Selling crypto for poundsDisposal (CGT)Capital gain = proceeds less allowable cost, matched by same-day, then 30-day, then Section 104 pool rules. Annual exempt amount applies; gains above it taxed at CGT rates.
Buying more of the same tokenAcquisition (pooling)Increases the Section 104 pool quantity and pooled allowable cost; future disposals deduct an average cost.
Crypto-to-crypto tradeDisposal (CGT)Disposal of the token given up at pound market value; a CGT event subject to the matching rules.
Selling and rebuying within 30 daysDisposal (30-day rule)The disposal is matched with the reacquisition under the bed-and-breakfasting rule, not the pool, limiting artificial loss crystallisation.
Staking or mining rewardsIncome receivedIncome tax (and possibly NICs) at market value on receipt; that value becomes the acquisition cost for a later CGT disposal.
AirdropsIncome or capital (fact-dependent)Often income where received in return for something; otherwise may have nil income with CGT on disposal. Depends on the facts.
Transferring between own walletsNo disposalNot a disposal; pooled cost continues. Fees may have their own treatment.

Forms and filing

Report capital gains on the SA108 Capital Gains Summary supplementary pages of the Self Assessment return, alongside any crypto-specific entries HMRC requires; report crypto income in the relevant income sections. Maintain records of every acquisition and disposal, the Section 104 pooled cost, and the pound values used. UK allowances and CGT rates change each tax year. Confirm the current annual exempt amount and rates with HMRC before filing.

Penalties

HMRC can charge penalties and interest for failure to notify, late filing, or inaccuracies, scaled by behaviour (from careless to deliberate and concealed). HMRC receives data from exchanges and runs crypto compliance campaigns, so undeclared gains are increasingly visible. This is general information, not tax advice.

Frequently asked questions

How does HMRC tax crypto in the UK?
HMRC treats cryptoassets as property. Most individuals pay Capital Gains Tax on disposals, computed using the Section 104 pool with same-day and 30-day matching rules. Some receipts (mining, staking, employment income, certain airdrops) are subject to Income Tax.
What is the Section 104 pool?
For each token you maintain a running pool of total quantity held and total allowable cost. Acquisitions add to the pool; disposals deduct an average (pooled) cost proportionate to the units sold, unless overridden by the same-day or 30-day rules.
What is the 30-day (bed-and-breakfasting) rule?
Disposals are matched first with same-day acquisitions, then with acquisitions in the following 30 days, before drawing from the Section 104 pool. It prevents selling to crystallise a loss and immediately rebuying at the same cost.
Where do I report crypto gains in the UK?
On the SA108 Capital Gains Summary pages of your Self Assessment return, with crypto income in the relevant income sections. Keep records of acquisitions, disposals, pooled cost and the pound values used.

Sources

References

The official United Kingdom documents behind this guide and behind Coinfig calculations for United Kingdom. Each title opens the dated copy Coinfig keeps, archived 2026-09-10, and the live source opens the authority's own page.

Start here

  1. Cryptoassets Manual (index) HM Revenue & Customs Live source

    The contents page of HMRC’s Cryptoassets Manual, which is where HMRC sets out how it reads each kind of crypto transaction.

  2. Taxation of Chargeable Gains Act 1992, section 104, share pooling: general interpretative provisions UK Parliament, via legislation.gov.uk Live source

    Section 104 of the Taxation of Chargeable Gains Act 1992, the share pooling rule that decides UK cost basis.

  3. Capital Gains Tax summary (SA108) 2025-26 form HM Revenue & Customs Live source

    The SA108 capital gains pages for the 2025 to 2026 tax year, the form your gains and losses are reported on.

  4. Capital Gains Tax summary notes (SA108 Notes) 2025-26 HM Revenue & Customs Live source

    HMRC’s notes for the same year, which explain what belongs in each box on the SA108.

  5. Self Assessment tax returns: deadlines HM Revenue & Customs, via gov.uk Live source

    The Self Assessment deadlines page, for when the return is due and when the tax has to be paid.

  6. Taxation of stablecoins (call for evidence outcome) HM Treasury and HM Revenue & Customs, via gov.uk Live source

    HMRC’s July 2026 outcome on taxing stablecoins, the most recent change to watch.

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