United Kingdom

How Capital Gains Tax works in the UK#

HMRC treats cryptocurrency as a chargeable asset for Capital Gains Tax. Every disposal — selling for pounds, swapping for another coin, or paying for something — is a chargeable gain or loss under the Taxation of Chargeable Gains Act 1992.

Unlike Canada (one pool, always) or the US and Australia (individual lots), the UK matches each disposal to its cost in three steps:

1. Same-day rule (s. 105) — same-day acquisitions first
2. 30-day rule (s. 106A) — then acquisitions in the next 30 days
3. Section 104 pool — whatever is left comes out of the pool at average cost

Example (Section 104 pool):

Date	Action	Quantity	Price (£)	Pool afterwards
1 Jan 2025	Buy 2.0 ETH	2.0	£6,000	2.0 ETH at £3,000 average
1 Feb 2025	Buy 3.0 ETH	3.0	£12,000	5.0 ETH at £3,600 average
1 Mar 2025	Sell 1.0 ETH	-1.0	£5,000	4.0 ETH at £3,600 average

Chargeable gain: £5,000 − (1.0 × £3,600) = £1,400

There were no same-day or 30-day acquisitions, so the whole disposal came out of the pool.

The three matching rules#

1. Same-day rule (s. 105)#

Every acquisition and disposal on the same day is pooled before matching. Buy 2 ETH at 9 am and sell 1 ETH at 5 pm, and the sale is matched to the morning’s purchase, not to the Section 104 pool.

2. 30-day rule (s. 106A), bed and breakfasting#

What the same-day rule leaves is matched to acquisitions in the next 30 days, looking forward only. This is the rule against selling at a loss and buying straight back. The window starts the day after the disposal: sell on 15 January and acquisitions from 16 January to 14 February are matched. When two disposals compete for one acquisition, the earlier disposal takes it.

3. Section 104 pool#

Whatever remains comes out of the Section 104 pool at the pool’s average cost per token. An acquisition that was matched by the same-day or 30-day rule is diverted; it never enters the pool.

The program applies all three in two passes, and the Audit Provenance report shows which rule matched each disposal.

The Annual Exempt Amount#

The first slice of your net gains each tax year is exempt from Capital Gains Tax. The program applies the figure for the year you calculate, and the table is the one it uses:

Tax year	Annual Exempt Amount
2024/25 onwards	£3,000
2023/24	£6,000
2020/21 to 2022/23	£12,300
2019/20	£12,000
2018/19	£11,700
2017/18	£11,300
2015/16 and 2016/17	£11,100
2014/15	£11,000
2013/14	£10,900
2011/12 and 2012/13	£10,600
2009/10 and 2010/11	£10,100

Only the gain above the amount is taxed. The program shows the deduction in the dashboard’s tax summary and on the SA108 report.

The SA108 report fills the Cryptoassets section HMRC added to the form for 2024/25: boxes 13.1 to 13.8 (number of disposals, proceeds, allowable costs, gains before losses, losses, and the claim, real-time-return and tax-paid boxes). The 2025/26 form keeps the same numbering.

What the UK doesn’t have#

• No wash-sale rule — the 30-day rule changes which cost a disposal takes, but it does not deny a loss
• No superficial-loss rule — nothing looks backward from a sale
• No lot tracking — one pool per asset, not individual lots
• No per-account tracking — cost is not kept per wallet or exchange
• No short-term or long-term classes — the rate does not depend on how long you held
• No holding-period discount — unlike Australia’s 50% discount

Prices and exchange rates#

Crypto prices come from CoinGecko in pounds for the past year. For older dates the program uses DefiLlama and Binance, which quote in US dollars, and converts at that day’s exchange rate. You can also import a price file or type a price yourself; the UK example set uses price files so that its figures reproduce to the penny.

References#

• TCGA 1992, s. 104 — the Section 104 holding
• TCGA 1992, s. 105 — the same-day rule
• TCGA 1992, s. 106A — the 30-day rule
• HMRC Cryptoassets Manual, CRYPTO22200 to CRYPTO22257 — the share-identification rules applied to cryptoassets
• HMRC Capital Gains Manual, CG51560 — the Section 104 pool
• Capital Gains Tax rates and allowances (gov.uk) — the Annual Exempt Amount and the rates by year, including the change for disposals from 30 October 2024