When you sell or swap crypto in the UK, the gain depends on which of your tokens HMRC treats as the ones you sold. You don’t get to pick. HMRC’s guidance applies three matching rules in a fixed order: the same-day rule, the 30-day rule and the Section 104 pool. This guide explains each rule, restates HMRC’s own worked examples with the figures, and shows how the result flows into your Self Assessment return.
What counts as a disposal
The matching rules only matter when there is a disposal. HMRC’s manual lists four common ones (CRYPTO22100):
- selling tokens for money;
- exchanging tokens for a different type of token, so a crypto-to-crypto swap counts;
- using tokens to pay for goods or services;
- giving tokens away, other than to a spouse or civil partner.
The same page says that moving tokens between wallets you control is not a disposal. That matters in practice. An exchange export often shows a withdrawal that looks just like a sale. If you don’t pair it with the matching deposit, the report can show a gain that never happened. Our guide to moving crypto between your own wallets covers how to fix that.
The three rules, in order
HMRC’s pooling guidance (CRYPTO22200) applies the rules separately for each type of token. Bitcoin has its own pool, Ether has its own, and so on. For each disposal, work down this list until every unit sold has been matched:
| Order | Rule | What it matches | Legal basis |
|---|---|---|---|
| 1 | Same-day rule | Tokens of the same type bought on the same day as the disposal | TCGA 1992 s105 |
| 2 | 30-day rule | Tokens of the same type bought in the 30 days after the disposal, earliest first | TCGA 1992 s106A |
| 3 | Section 104 pool | Whatever is left, at the pool’s average cost | TCGA 1992 s104 |
Acquisitions that aren’t matched under the first two rules go into the pool. CRYPTO22200 also notes that non-fungible tokens are separately identifiable, so they aren’t pooled and the matching rules don’t apply to them.
The UK crypto tax calculator runs these rules for you. Each disposal in the report lists every match, the rule that made it and the HMRC page it comes from, so you can check the working line by line.
The Section 104 pool
The pool is the default. All your tokens of one type that aren’t matched elsewhere sit in a single pot with a single total cost. When you sell from the pool, you take a share of that total cost in proportion to the number of tokens sold. HMRC works through this in its first example.
HMRC example 1: a basic pool disposal (CRYPTO22251)
- The pool holds 100 token A with a cost of £1,000.
- On 18 September, 50 more token A are bought for £125,000. The pool is now 150 tokens and £126,000.
- On 1 December, 50 token A are sold for £300,000.
- Cost taken from the pool: £126,000 × 50 ÷ 150 = £42,000.
- Gain: £300,000 − £42,000 = £258,000.
- The pool is left with 100 token A and a cost of £84,000.
Source: CRYPTO22251.
Notice what the pool does. The cheap early tokens and the expensive later ones are blended. You can’t say you sold the £10 tokens or the £2,500 tokens. Every token in the pool carries the same average cost.
The same-day rule
Under the same-day rule, all the tokens of one type you buy on a day are treated as a single acquisition. All those you dispose of that day are treated as a single disposal. The two are then matched first, before anything else (CRYPTO22200).
HMRC example 2: the same-day rule (CRYPTO22252)
- The pool holds 5,000 token B with a cost of £500.
- On one day: in the morning 1,000 are sold for £800; in the afternoon 1,600 are bought for £1,000; in the evening 500 are sold for £600.
- The two sales become one disposal of 1,500 tokens for £1,400.
- They’re matched with the same-day purchase: cost £1,000 × 1,500 ÷ 1,600 = £938 (HMRC rounds to the pound).
- Gain: £1,400 − £938 = £462.
- The 100 unmatched tokens from the purchase join the pool with a cost of £62, giving 5,100 tokens and £562.
Source: CRYPTO22252.
The order within the day doesn’t matter. The morning sale came before the purchase, yet it was still matched with it.
What “same day” means for timestamps
We couldn’t find a time zone in HMRC’s pooling guidance. That leaves a practical question, because most exchanges export timestamps in UTC. During British Summer Time, a trade at 11:30pm in London is already the next day in UTC. CryptoTaxOwl uses the UK local date (Europe/London) to decide which day a trade falls on. That is our documented choice, not an HMRC rule. If you or your adviser take a different view, the matching on the edges of a day may change. How it works explains how we handle dates.
The 30-day rule
After same-day matching, any part of a disposal that is still unmatched is matched with tokens of the same type bought in the 30 days that follow it. The earliest acquisition is matched first, and disposals are dealt with in date order (TCGA 1992 s106A; CRYPTO22200). The effect is that selling and quickly buying back doesn’t give you a gain or loss measured against the pool.
HMRC example 3: the 30-day rule (CRYPTO22253)
The pool holds 2,000 token C with a cost of £1,000. Then:
| Date | Transaction | Tokens | Amount |
|---|---|---|---|
| 31 March | Sell | 1,000 | £400 |
| 20 April | Sell | 500 | £150 |
| 21 April | Buy | 700 | £175 |
| 28 April | Buy | 500 | £100 |
| 1 May | Buy | 500 | £150 |
- 31 March sale of 1,000. The first purchase in the next 30 days is 21 April: all 700 tokens, cost £175. The next is 28 April: 300 of the 500, cost £100 × 300 ÷ 500 = £60. Gain: £400 − £175 − £60 = £165.
- 20 April sale of 500. What’s left of the 28 April purchase is 200 tokens, cost £40. The rest comes from 1 May: 300 of the 500, cost £150 × 300 ÷ 500 = £90. Gain: £150 − £40 − £90 = £20.
- The pool. No tokens were taken from it. The 200 unmatched tokens from 1 May join it at a cost of £60, giving 2,200 tokens and £1,060.
Source: CRYPTO22253.
Two points stand out. First, the earlier disposal gets first claim on the later purchases. Second, the 31 March sale and the April purchases sit on either side of 5 April, the end of the UK tax year. The matching still applies, so a sale near the end of a tax year can depend on purchases made in the next one. Keep that in mind if you file early.
Allowable costs and losses
Costs you can deduct
HMRC’s list of allowable costs for cryptoassets (CRYPTO22150) includes:
- what you originally paid for the tokens, in pounds sterling;
- transaction fees paid to have a transaction added to the ledger;
- advertising to find a buyer or seller;
- professional costs of drawing up a contract for the acquisition or disposal;
- costs of making a valuation or apportionment to work out the gain.
The same page says some costs are not allowable. These include costs already deducted against Income Tax, mining equipment and electricity, and fees for depositing or withdrawing pounds on an exchange. In a pool, an allowable acquisition fee is added to the pool’s cost. A disposal fee is deducted when you work out that disposal’s gain.
Losses
A disposal can produce a loss. gov.uk says losses are deducted from gains in the same tax year. Losses from earlier years can then be used if your remaining gain is still above the tax-free allowance, and anything unused carries forward. You can report a loss up to 4 years after the end of the tax year in which you disposed of the asset (gov.uk: losses). If you’ve lost access to tokens for good, HMRC explains when a negligible value claim may apply (CRYPTO22400).
To try a single trade before importing everything, the crypto capital gains calculator works out one disposal with fees.
Do I need to report? The £3,000 allowance and the £50,000 proceeds rule
The UK tax year runs from 6 April to 5 April. The Capital Gains Tax annual exempt amount for individuals is £3,000 for 2024 to 2025, 2025 to 2026 and 2026 to 2027, down from £6,000 in 2023 to 2024 (HMRC rates and allowances).
The rates for gains on assets such as cryptoassets changed part-way through 2024 to 2025:
| Period | Rates for individuals |
|---|---|
| 6 April 2024 to 29 October 2024 | 10% and 20% |
| 30 October 2024 to 5 April 2025 | 18% and 24% |
| 6 April 2025 to 5 April 2026 | 18% and 24% |
Source: HMRC rates and allowances. Which rate applies depends on your income. gov.uk explains how the basic rate band affects it (gov.uk: CGT rates). For 2024 to 2025, this means you need to know which disposals happened before 30 October 2024 and which happened on or after it.
Paying tax and reporting are different questions. gov.uk says you need to report if your total taxable gains are above your allowance. It also says that if you’re registered for Self Assessment, you need to report your gains if the total you sold assets for was more than £50,000, for 2023 to 2024 onwards (gov.uk: work out if you need to pay). In a busy trading year, proceeds can pass £50,000 while net gains stay small. Swaps are disposals too, so every swap adds to your proceeds total.
What this means for your return
If you file a Self Assessment return, gains and losses go on the capital gains summary pages, SA108 (SA108). For the 2025 to 2026 tax year, gov.uk gives 31 January 2027 as the deadline for an online return and for paying the tax (gov.uk: deadlines). The crypto tax deadline calendar lists the key dates.
In practice, the figures you need are:
- the number of disposals in the tax year;
- total disposal proceeds, in pounds;
- total allowable costs, including fees;
- gains before losses, and losses.
The UK report produces each of these with a “where this goes” label, plus a Section 104 pool statement for each token. The statement shows the opening position, every movement and the closing position. Keep it with your records. HMRC’s guidance expects you to keep acquisition cost records for each token type (CRYPTO22200).
If your exchange files are in different layouts, the crypto CSV converter turns them into one standard file first. Then load it into the UK calculator.
Honest limits
- We report; we don’t advise. The calculator applies HMRC’s published matching rules to the data you give it. It can’t tell whether you’re trading as a business, whether you’re UK resident, or whether a transaction is a gift. If you’re unsure, speak to a qualified adviser.
- Garbage in, garbage out. Missing purchases, unmatched transfers or wrong sterling values will change the pool. Our review queue lists anything that needs your decision rather than guessing.
- Rounding. HMRC rounds intermediate costs to the pound in its examples. The calculator keeps full precision, so totals can differ from a hand calculation by a pound or so.
- The time zone choice. As explained above, the UK local date is our choice where the guidance is silent.
- Out of scope. DeFi lending and liquidity pools, NFTs, and margin or derivatives trading aren’t modelled.
Sources
- CRYPTO22100 - Cryptoassets for individuals: Capital Gains Tax: what is a disposal (HMRC), retrieved 7 October 2026
- CRYPTO22150 - Cryptoassets for individuals: Capital Gains Tax: allowable expenses (HMRC), retrieved 7 October 2026
- CRYPTO22200 - Cryptoassets for individuals: Capital Gains Tax: pooling (HMRC), retrieved 7 October 2026
- CRYPTO22251 - Cryptoassets for individuals: Capital Gains Tax: pooling examples: example 1 - basic section 104 pool disposal (HMRC), retrieved 7 October 2026
- CRYPTO22252 - Cryptoassets for individuals: Capital Gains Tax: pooling examples: example 2 - application of the same day rule (HMRC), retrieved 7 October 2026
- CRYPTO22253 - Cryptoassets for individuals: Capital Gains Tax: pooling examples: example 3 - application of the 30 day rule (HMRC), retrieved 7 October 2026
- CRYPTO22400 - Cryptoassets for individuals: Capital Gains Tax: losing private keys (HMRC), retrieved 7 October 2026
- Taxation of Chargeable Gains Act 1992, section 104: Share pooling: general interpretative provisions (legislation.gov.uk), retrieved 7 October 2026
- Taxation of Chargeable Gains Act 1992, section 105: Disposal on or before day of acquisition of shares and other unidentified assets (legislation.gov.uk), retrieved 7 October 2026
- Taxation of Chargeable Gains Act 1992, section 106A (legislation.gov.uk), retrieved 7 October 2026
- Capital Gains Tax rates and annual tax-free allowances (HMRC), retrieved 7 October 2026
- Capital Gains Tax: what you pay it on, rates and allowances: Capital Gains Tax rates (gov.uk), retrieved 7 October 2026
- Capital Gains Tax: what you pay it on, rates and allowances: Work out if you need to pay (gov.uk), retrieved 7 October 2026
- Capital Gains Tax: what you pay it on, rates and allowances: Losses (gov.uk), retrieved 7 October 2026
- Self Assessment: Capital gains summary (SA108) (HMRC), retrieved 7 October 2026
- Self Assessment tax returns: Deadlines (gov.uk), retrieved 7 October 2026
- Check if you need to pay tax when you receive cryptoassets (HMRC), retrieved 7 October 2026
Frequently asked questions
Is swapping one cryptoasset for another taxable in the UK?
It can be. HMRC lists exchanging tokens for a different type of token as a disposal for Capital Gains Tax, in the same way as selling for pounds (CRYPTO22100). You need the sterling value of what you gave up to work out the gain.
Can I use FIFO instead of the Section 104 pool?
Not for fungible tokens held as an individual investor. HMRC’s guidance applies the same-day rule, then the 30-day rule, then the Section 104 pool (CRYPTO22200). The order is set out in that guidance rather than chosen by you. Our cost basis methods guide compares how other countries do it.
Does moving tokens between my own wallets count as a disposal?
No. HMRC says moving tokens between wallets you control isn’t a disposal (CRYPTO22100). Any fee paid in tokens for the transfer needs separate thought. Our guide to transfers between your own wallets explains how to stop transfers showing up as sales.
Which time zone decides the “same day”?
We couldn’t find a time zone stated in HMRC’s pooling guidance. CryptoTaxOwl uses the UK local date (Europe/London). That is our documented choice, and the How it works page says so. Exchange exports are often in UTC, so a late-evening trade can fall on a different date in each.
How are staking rewards and airdrops treated?
HMRC has separate guidance on when tokens you receive are taxed. Our staking and airdrops guide covers it, and the staking income calculator totals rewards at their value when received.
Do I have to report if my gains are under £3,000?
Possibly. If you’re registered for Self Assessment, gov.uk says you need to report gains in your return if the total you sold assets for was more than £50,000 (from 2023 to 2024 onwards), even when no tax is due (gov.uk).
This guide explains the rules in general terms. It isn’t tax advice. Spotted something out of date? Email errors@cryptotaxowl.com and we’ll check it against the source.