This is the most common misconception in UK crypto tax — and the one most likely to result in HMRC penalties. Swapping BTC for ETH is a taxable disposal even though no GBP ever changed hands.
Why crypto-to-crypto swaps are taxable in the UK
HMRC treats every cryptocurrency as a distinct asset. When you exchange BTC for ETH, two things happen simultaneously: you have disposed of BTC (triggering CGT on any gain since you acquired it) and acquired ETH (at its GBP value at the time of the swap, which becomes your cost basis).
The fact that you received crypto rather than cash makes no difference to HMRC. A disposal is a disposal whenever you give up ownership of an asset.
Worked example
Acquisition: You bought 1 BTC for £20,000 in 2021.
Swap: In 2024, when BTC is worth £45,000, you swap 1 BTC for 15 ETH (also worth £45,000).
BTC disposal: Proceeds £45,000 − Cost £20,000 = Gain of £25,000.
ETH acquisition: You now own 15 ETH with a total cost basis of £45,000 (£3,000 per ETH).
What value to use
Use the GBP market value of the asset you are giving up at the time of the swap. If BTC is worth £45,000 at that moment, your proceeds are £45,000 — regardless of how much ETH you received or what it is worth now.
If the swap involves a USD-denominated pair (BTC/USDT for example), convert the USD value to GBP using the exchange rate at the exact date and time of the trade.
DEX swaps, wrapped tokens, and DeFi
Swaps on decentralised exchanges (Uniswap, 1inch, Curve, etc.) are treated exactly the same as centralised exchange swaps. Each swap is a disposal of the asset being sold. HMRC does not distinguish between CEX and DEX for tax purposes.
Wrapping and unwrapping tokens (ETH to WETH and back) is a grey area — HMRC has not provided definitive guidance on whether this constitutes a disposal. The conservative treatment is to treat it as taxable; many professional advisers take this position.
Many exchanges only export GBP-denominated trade history, causing users to miss all BTC/ETH, BTC/USDT, and other non-GBP pairs. These are all taxable. If you only exported your “GBP transactions” you have likely missed most of your taxable events.
Frequently asked questions
Does swapping ETH for a stablecoin (USDT, USDC) count as a disposal?
Yes. Swapping ETH for USDT is a disposal of ETH. USDT is a separate asset from ETH. If you made a gain on the ETH since you acquired it, that gain is taxable. The fact that USDT is pegged to USD does not change the tax treatment.
What if I lost money on the swap?
A loss-making swap is still a taxable event — but it produces a loss rather than a gain. That loss reduces your total gains for the year and can be carried forward. You should report the loss even if you have no gains to offset, to preserve it for future years.
I made thousands of small swaps on a DEX. Do I need to report every one?
In principle yes — every swap is a separate disposal event. In practice, you need the aggregate figures (total gains, total losses) to report on SA108, so you need a tool that can process your full transaction history. Reporting a summary rather than each individual trade is acceptable as long as the totals are correct.
What about liquidity pool transactions — adding and removing liquidity?
Adding liquidity to a pool (depositing ETH and USDC, for example, and receiving LP tokens) may be treated as a disposal of the deposited assets and acquisition of the LP tokens. Removing liquidity reverses this. HMRC's guidance on DeFi is evolving and this area is genuinely uncertain — professional advice is recommended for significant DeFi activity.
If I swap crypto and then immediately swap it back, do I have two taxable events?
Yes. Each swap in a sequence is a separate disposal. Swapping BTC → ETH → BTC creates two taxable events: one on the BTC disposed of in the first swap, one on the ETH disposed of in the second. There is no netting between them.
How does the 30-day rule apply to swaps?
The 30-day rule applies to the same asset. If you dispose of BTC and reacquire BTC within 30 days, the rule applies. If you swap BTC for ETH, the 30-day rule does not apply to the BTC disposal because you acquired ETH, not BTC.
General information only. Consult a qualified adviser.