CryptoTax UK · Guide
Same-Day Rule for Crypto UK — HMRC Guide
HMRC's same-day rule is the first of three matching rules that must be applied before drawing from the Section 104 pool. This guide explains exactly how it works with worked examples. Educational only — not tax advice.
Calculate using HMRC matching rules →What is the same-day rule?
If you dispose of a crypto asset and acquire the same asset on the same day, HMRC matches the disposal with that day's acquisition first. The cost of the disposal is the cost of the same-day acquisition (not the Section 104 pool average). This rule applies regardless of whether the buy happened before or after the sell on that day.
Worked example
You hold 1 BTC in your Section 104 pool at an average cost of £20,000. On 1 March 2026 you sell 0.5 BTC for £25,000 and also buy 0.5 BTC for £24,000 on the same day. Under the same-day rule, the disposal is matched with the same-day acquisition at £24,000. Gain = £25,000 - £24,000 = £1,000.
Why does the same-day rule exist?
The same-day rule (and the 30-day rule) exist to prevent tax avoidance through bed-and-breakfasting — selling an asset to crystallise a loss and immediately rebuying to reset the cost basis.
Frequently asked questions
Does the same-day rule apply to different exchanges?
Yes — HMRC looks at the date of the transaction across all exchanges, not the platform. If you sell BTC on Coinbase and buy BTC on Binance on the same day, the same-day rule still applies.
What if I only partially match?
If your same-day purchase is smaller than your disposal, match what you can with the same-day purchase and draw the remainder from the Section 104 pool.
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Calculate using HMRC matching rules →Educational guidance only. CryptoTax UK is not a regulated tax adviser and the information above does not constitute tax, legal or financial advice. Always confirm your specific position with HMRC or a qualified accountant before filing.