How to Report Crypto on Your UK Self Assessment Tax Return

Filing crypto on your UK Self Assessment can feel overwhelming, but it is more straightforward than most people think. Here is exactly where crypto goes on your tax return for the 2025/26 tax year.

Do you need to file?

You need to report crypto on Self Assessment if your total disposal proceeds exceed £12,000 (four times the £3,000 CGT allowance), or if you have a net capital gain above £3,000, or if you received crypto income (mining, staking, airdrops) above the £1,000 trading allowance. Even if you only made losses, reporting them allows you to carry them forward.

Capital gains: SA108

Crypto capital gains go on the Capital Gains supplementary pages (SA108). You need to complete: Box 20 — number of disposals. Box 21 — total disposal proceeds. Box 22 — allowable costs (your total cost basis). Box 23 — gains before losses. Box 24 — losses. Box 25 — net gains. You do not need to list every individual transaction — just the totals. However, you must keep detailed records that support your figures.

Income: SA103 or SA106

Crypto received as income (mining, staking, airdrops, employment) goes in different places depending on the type. Trading income (if mining/staking is a business) goes on SA103 (Self-Employment). Miscellaneous income (hobby mining, staking rewards, airdrops) goes on SA106 (Additional Information) under "Other taxable income."

The process

Register for Self Assessment if you have not already — this can take a few weeks. Log into your HMRC online account. Start a new return for the relevant tax year. Complete the main return, then add the Capital Gains and/or Additional Information supplementary pages. Review everything carefully. Submit online by 31 January following the end of the tax year. Pay any tax owed by the same deadline.

Common mistakes

Forgetting token-to-token swaps are disposals. Using FIFO instead of Section 104 pooling. Not reporting DeFi transactions. Forgetting to include gas fees as allowable costs. Missing the 30-day bed-and-breakfasting rule. Not reporting losses (which means losing the ability to carry them forward).

Making it easy

CryptoLens generates a complete tax summary with all the figures you need for SA108. The Pro plan exports a detailed PDF showing every disposal, your Section 104 pools, and the calculations behind each figure — ready to hand to your accountant or use directly for filing.