UK Crypto Self Assessment 2026/27: Step-by-Step Walkthrough

UK crypto tax is enforced via HMRC's Cryptoassets Manual, last materially updated December 2023 plus tweaks for DeFi and NFTs through 2025. The walkthrough below covers a 2026/27 tax return for a typical crypto holder.

Step 1: Decide whether you have income or capital gains

HMRC treats most crypto activity as capital gains (CGT regime). A few activities fall under income tax (PAYE / Self Assessment income box).

Capital Gains category:

• Buying crypto and selling for fiat
• Swapping one crypto for another
• Spending crypto on goods or services
• Gifting crypto (except to spouse - that's a no-gain-no-loss transfer)

Income category:

• Mining rewards (treated as miscellaneous income at the market value at receipt)
• Staking rewards from Proof-of-Stake protocols (HMRC's view per CRYPTO21200)
• Yield farming returns from DeFi protocols
• Crypto received as employment payment (PAYE)
• Airdrops where you provided "service" to receive (income); pure airdrops (no service) = treated as zero-cost-base asset, CGT on later disposal

In practice most retail holders have CGT-only activity.

Step 2: Compute disposals using share-matching rules

HMRC requires the Section 104 pool approach for fungible crypto holdings, with two exception rules:

1. Same-day rule - any acquisitions on the same day as a disposal are matched first.
2. Bed and breakfast rule (30-day) - any acquisitions in the 30 days following a disposal are matched second.
3. Section 104 pool - remaining acquisitions form a single pool with an average cost per coin. Disposals draw from this pool at the average cost.

Example - ETH transactions in 2026/27:

• 1 April 2026: bought 5 ETH at £1,800 each = £9,000 cost
• 1 June 2026: bought 5 ETH at £2,200 each = £11,000 cost (pool now 10 ETH, total cost £20,000, average £2,000/ETH)
• 1 August 2026: sold 4 ETH at £2,800 each = £11,200 proceeds
• 1 September 2026: bought 2 ETH at £2,400 (within 30 days of 1 Aug disposal - bed and breakfast)

The 1 Aug disposal of 4 ETH matches:

• 2 ETH against the 1 Sep purchase (bed and breakfast, cost £4,800)
• 2 ETH against the Section 104 pool (average £2,000/ETH, cost £4,000)
• Total cost matched: £8,800
• Gain: £11,200 - £8,800 = £2,400

After this disposal the pool has 6 ETH (10 - 4 = 6) at remaining cost £20,000 - £4,000 = £16,000 (the bed-and-breakfast matched coins are removed from the pool calculation).

Step 3: Allowable costs

Deductible from disposal proceeds:

• Original acquisition cost in GBP
• Transaction fees ("gas" / network fees) on acquisition AND disposal
• Exchange withdrawal fees
• Software costs proportionate to crypto tracking (e.g. CoinTracker subscription)

NOT deductible:

• Hardware wallet purchase (HMRC view: capital asset, separate)
• Time spent researching trades
• Professional advice fees (legal/accountancy specifically related to crypto are typically deductible against income, not CGT gain)

Step 4: Use the £3,000 annual CGT allowance

Each person has a £3,000 annual exempt amount for 2026/27 (down from £6,000 in 2023/24, £12,300 pre-2023). Gains below £3,000 in total (across ALL CGT assets, not just crypto) - no tax.

Above £3,000:

• Basic-rate slice: 18%
• Higher / additional rate slice: 24%

The basic/higher boundary is your normal Income Tax band - so a £50,000 salary earner has £270 of basic-rate CGT space (£50,270 higher-rate threshold - £50,000 = £270) and the rest at 24%.

Step 5: Compute and report on SA108

The Capital Gains Summary supplementary page (SA108) requires:

• Total proceeds from cryptoasset disposals
• Total allowable costs (acquisition + fees)
• Total gains
• Total losses
• Annual exempt amount used
• CGT due

Plus the "Other property, assets and gains" section requires you to enter the number of disposals + the proceeds + the costs + the gains.

You don't need to submit transaction-by-transaction detail to HMRC, but you must keep contemporaneous records for 6 years in case of investigation.

Step 6: DeFi + staking income

For income-side reporting (separate from CGT):

• Staking rewards: report market value at moment of receipt as miscellaneous income on the "Other UK income" page (SA100 box 17). Income Tax at marginal rate applies.
• Liquidity pool tokens / wrapped tokens: HMRC's December 2022 consultation suggested treating LP token receipt as a disposal of the underlying. Position has not been fully legislated but is being treated as the operating assumption. Watch for Finance Bill 2026/27 updates.
• Airdrops with service requirement (e.g. follow Twitter, retweet): income at market value at receipt.
• Pure airdrops (no service): zero cost base; CGT only on later disposal.

Step 7: Losses

Losses on crypto disposals can be set against:

• Other CGT gains in the same year
• Future year CGT gains (must be reported via Self Assessment within 4 years of the loss being made)

Losses cannot be set against income.

A loss being "negligible value" claim can crystallise a loss without selling - useful for tokens that have gone to zero on rugged protocols. Submit via the "claims and elections" section.

Step 8: Deadlines + penalties

• File + pay 2026/27 Self Assessment by 31 January 2028.
• Late filing: £100 immediate penalty + £10/day after 3 months + 5% of tax due after 6 months.
• Late payment: 5% of unpaid tax after 30 days + 5% after 6 months + 5% after 12 months.
• Interest charges on unpaid tax from 1 February 2028: HMRC late payment interest = Bank Rate + 4 percentage points (post-6-April-2025 rule per Finance Act 2024).

Common mistakes

1. Forgetting crypto-to-crypto swaps are disposals. Every swap = CGT event. Hundreds of small DEX swaps = hundreds of tiny gains/losses.
2. Missing the 30-day bed-and-breakfast rule when buying back after a sale.
3. Not tracking gas fees in GBP at time of transaction - the rate moves materially day-to-day.
4. Treating staking rewards as CGT instead of income - HMRC position is income (CRYPTO21200).
5. Forgetting USDT/USDC stablecoin swaps - they are still disposals even though the price barely moves.
6. Wallet-to-wallet self-transfers mistakenly reported as disposals - moving between wallets you own is NOT a disposal.

Tools

• Crypto CGT calculator - models the share-matching rules
• Self-employed calculator - if crypto activity is your trade (e.g. day trading, professional staker - HMRC trade-vs-investment tests apply)
• Salary calculator - main engine for combining crypto with PAYE income

Specialist crypto tax software (CoinTracker, Koinly, CoinLedger, Recap) automates the share-matching - typically £50-£200 for the year. Worth it if you have >50 transactions.

Not tax advice. HMRC's position on emerging DeFi mechanisms (lending, borrowing, liquid staking, NFT-bound assets) continues to evolve. Specialist advice recommended for complex DeFi activity.