A disposal happens when crypto leaves the taxpayer's ownership. HMRC values that disposal at the market price at the exact disposal time in UK local time. Use the executed trade price for exchange sales. For non‑trade transfers use a documented mid‑market or reasoned fair value within a short window. Apply the same‑day, 30‑day and Section 104 pooling rules to decide which acquisition is matched.
Why Valuation & Date of Disposal Rules matter
This explains how date and value change tax outcomes.
HMRC charges Capital Gains Tax on the date of disposal and the value at that moment. The gain equals proceeds in GBP minus the allowable acquisition cost in GBP. Using the wrong date or value can move a gain into a different tax year. That change can alter tax by thousands of pounds.
HMRC's matching rules stop simple timing tricks. The same‑day rule, the 30‑day rule and pooling force specific acquisitions to match disposals. Those rules create strict record needs and set clear valuation methods.
Poor timestamp handling is the most common cause of wrong CGT on crypto. Conservative, auditable records cut the risk in an HMRC enquiry.
Pause to check timestamps and sources now.
Caseload and exceptions
This summarises when CGT rules do not apply or change.
Most private investor disposals trigger CGT. But where activity looks like a trading business, HMRC treats profits as Income Tax. Work frequency, organisation and commercial motive are the main trading tests. If HMRC treats activity as trading, the disposal timing and valuation approach change.
Income events such as staking rewards and many airdrops are taxable as income when received. If tokens were taxed on receipt, later disposals can still create CGT. In those cases the base cost starts at the income value used at receipt.
Non‑resident taxpayers generally fall outside UK CGT for personal crypto. Exceptions exist for UK situs assets and for temporary non‑residence rules. Those situations need specialist advice.
An expert view: many taxpayers misclassify frequent trading as investing. That mistake can double their tax bill.
Pause and confirm whether activity looks like trading.
How HMRC values cryptocurrency for tax purposes
This states the valuation hierarchy HMRC accepts.
In valuation terms, HMRC expects the market value at disposal. Market value is the price a willing buyer and seller would agree. For liquid markets the quoted price at the transaction timestamp is primary.
Where no liquid market exists, HMRC accepts a reasoned hierarchy. Practical hierarchy options are: last trade on a reliable exchange close to the timestamp; mid‑market using bid/ask within the window; or a reasoned fair value backed by comparables or OTC evidence. If a model is used, the taxpayer must keep the model, assumptions, inputs and sources for HMRC to review.
For illiquid tokens the common market practice is an observation window of between 1 and 7 days centered on the trade. The nearest timestamp within that window is preferred. That practice reflected market behaviour in recent years.
According to HMRC guidance (2024), valuations must be auditable and the valuation method recorded. The FCA and others noted retail crypto ownership estimates in recent years rose to about 2–4 million UK adults. That growth has increased HMRC scrutiny on reporting.
💡 Consejo
Record the UTC timestamp, the exchange's GMT/BST conversion, and a screenshot of the order book or trade blotter within 24 hours.
Timestamps decide matching, the tax year and which matching rule applies. A reproducible process is essential to validate the exact disposal time. Best practice is to record the raw timestamp from the source, the reported timezone and the API server time or block timestamp. Save any millisecond field, a screenshot of the trade line showing time, trade id and order id, and the raw CSV/JSON export.
When on‑chain and off‑chain sources differ, prefer the blockchain block timestamp for on‑chain events. Prefer the exchange trade API timestamp for off‑chain trades. Convert every raw time to UK local time for same‑day and 30‑day matching. Remember UK date boundaries run from midnight to midnight UK local time.
If an exchange reports UTC, convert it to UK local time and show the conversion method. If an exchange gives only local server time with unknown offset, find the API metadata or use the exchange's published timezone. If uncertainty remains, keep both raw and converted times. Add a short reconciliation note in the audit file explaining the choice.
Pause and keep both raw and converted times in records.
Calculating market value on the valuation date
This gives a step by step method to find the market value at disposal.
Step 1 Record the disposal timestamp in UTC and convert it to UK time. The taxpayer must store the original UTC time from the exchange or wallet. Converting incorrectly will place the disposal in the wrong tax day.
Step 2 Capture the trade record. For exchange trades use the exchange CSV or trade receipt. For on‑chain trades use the transaction hash, block timestamp, and the on‑chain amount. For off‑chain or OTC trades collect both counterparties' signed confirmation.
Step 3 Select the valuation price. If the trade happened on an exchange, use the executed price as the market value. If the transfer did not involve a trade price, sample the best available quote in a 5‑minute window around the UTC timestamp and use the mid‑market price as the value.
Step 4 Convert to GBP. Use a reliable FX source and the market rate at the disposal timestamp. The taxpayer should choose a single FX source for the whole tax return and stick to it. Common choices include the Bank of England midday rates or exchange rates from the principal exchange used for the trade.
Step 5 Document the method. Each disposal record must include source links, screenshots, and CSV references. HMRC often asks for a clear chain from wallet to GBP value.
Example calculation same day disposal
A taxpayer sells 0.5 BTC at 13:07:12 UTC on 5 April 2024 on ExchangeX for 15,000 USDT per BTC. ExchangeX provides a trade CSV showing execution at 15,000 USDT. The taxpayer uses ExchangeX USD/GBP rate at 13:07:12 UTC of 0.80. Calculation: 0.5 × 15,000 = 7,500 USDT. GBP value = 7,500 × 0.80 = £6,000. That GBP figure is the disposal proceeds for CGT purposes on 5 April 2024.
Example calculation transfer without trade
A taxpayer moves 10,000 tokens of TokenZ from WalletA to WalletB at 22:45 UTC on 12 March 2024 with no trade. TokenZ is thinly traded. The taxpayer finds a last trade on a reputable exchange 2 hours earlier at 0.12 GBP. The taxpayer also records bid/ask quotes showing 0.11/0.13 in a 1‑hour window. The chosen valuation is the mid‑market 0.12 GBP giving proceeds value 10,000 × 0.12 = £1,200. The taxpayer stores screenshots and the exchange CSV.
Practical worked examples make the rules tangible. Example A — exchange→exchange: Alice transfers 1 ETH from ExchangeA to ExchangeB and sells it immediately on ExchangeB at 14:02:30 UK time on 10 July 2024 for 1,800 USDT. ExchangeB CSV shows executed price 1,800 USDT and ExchangeB USD/GBP rate at that timestamp 0.78. Proceeds = 1 × 1,800 = 1,800 USDT → GBP = 1,800 × 0.78 = £1,404. If the matching acquisition was 1 ETH bought on ExchangeA at 13:50:00 the same UK date, the same‑day rule applies and that acquisition cost is matched. Example B — wallet→wallet transfer: Bob moves 500 TokenX between his own wallets at 23:50 UTC on 29 March (BST in force). No sale occurs; this is not a disposal for CGT, but the transfer timestamp determines which pool the coins sit in for later disposals. Record TX hash, block timestamp and a snapshot of the wallet balance. Example C — crypto→crypto swap: Claire swaps 2 BTC for 40 ETH on a DEX at 09:15:10 UK time. Treat this as a disposal of BTC at the market value of BTC in GBP at 09:15:10; if the DEX provides a trade price in ETH only, sample the BTC/GBP price on a reliable exchange within a defined window (e.g. ±5 minutes) and document the chain of conversions. Each worked example should appear in the ledger with timestamp, original currency proceeds, FX chain and matching rule used.
Pause and attach trade receipts to each ledger line.
Which exchange rate to use on disposal date
This clarifies FX choice and rules on consistency.
The taxpayer must convert crypto proceeds to GBP at the market rate on the disposal timestamp. HMRC accepts several reputable FX sources. The key rule is to stay consistent across the tax return.
Common practical choices are the Bank of England noon rate or the exchange rate from the venue that executed the trade. If the exchange rate is used, capture the exchange's GBP pair price at the timestamp. If the Bank of England rate is used, show how the trade currency converted to GBP when the trade settled in USD or stablecoin.
Use the same FX source for the whole tax year. Switching sources without a clear reason invites HMRC questions. If a disposal spans multiple currencies, show the conversion chain with timestamps and sources.
⚠️ Atención
If the disposal used a stablecoin with fluctuating peg, do not assume 1:1 to GBP. Verify the stablecoin's USD price at the disposal timestamp and convert using the agreed chain of rates.
When no liquid market price exists, use a documented, auditable valuation method instead of an ad hoc figure. Step 1 define the observation window and justify length. Step 2 compile market evidence including last trades, bid/ask spreads, OTC confirmations and comparable tokens. Step 3 calculate a baseline price such as VWAP across venues. Step 4 apply liquidity and execution adjustments and document the rationale. Step 5 reconcile any OTC evidence and prefer contemporaneous bilateral proof where it is arm’s‑length. Step 6 prepare a short valuation memo listing inputs, formulas and a sensitivity table.
Example: a taxpayer holds 10,000 TokenY with last on‑book trade 0.50 GBP two days earlier and an OTC bid at 0.40 GBP same day; volume on‑book is 100 TokenY. Baseline VWAP = 0.50; apply a 20% liquidity discount = 0.40 GBP → value = 10,000 × 0.40 = £4,000. Save evidence: order book snapshots, OTC confirmation, calculation sheet and the memo so HMRC can reproduce the logic.
Pause and save a short valuation memo for illiquid assets.
Capital gains pooling identification and valuation rules
This explains same‑day, 30‑day and pooling and how to apply them.
The principal difference between normal matching and the special rules is that HMRC forces which acquisition is matched to a disposal. The order of matching is fixed and must be applied strictly.
The rules are: Same‑day rule Any acquisitions of the same asset made on the same UK date as the disposal are matched first. 30‑day rule If no same‑day acquisition exists, acquisitions in the 30 days after the disposal are matched next. Section 104 pooling If neither same‑day nor 30‑day matches apply, all remaining holdings of that asset held before the disposal sit in the Section 104 pool and are matched using a pooled average cost per unit.
When applying the 30‑day rule, use UK local dates and times. When computing a pool cost, add purchase costs and allowable incidental costs. Divide by total units to get the pool unit cost. For a mixed set of acquisitions include on‑chain receipts and exchange purchases in the pool unless they are matched by same‑day or 30‑day rules.
An important exception is where tokens are part of a trading business or are not the taxpayer's assets. In those cases the pooling rules can be inappropriate. Also certain tokenised securities might follow different rules because of underlying legal forms. Those edge cases need specialist advice.
Debate exists about which timestamp to prefer for cross‑venue moves. Some professionals always use the blockchain timestamp for on‑chain events. Others prefer the exchange trade timestamp for off‑chain trades. Expert judgment is needed. The recommended practical approach is to prefer chain timestamps for on‑chain disposals and exchange API timestamps for off‑chain trades, and to document the choice.
One final practical note: the matching rules often move small gains into another tax year. That effect can change whether the gain uses a taxpayer's annual exemption. Plan record keeping accordingly.
Pause and confirm which acquisitions are same‑day before pooling.
