Crypto investors often do not realise that swapping one cryptocurrency for another can trigger Capital Gains Tax, even when no cash ever change hands. It does not feel as if you've exited your crypto investment as a whole, but HMRC sees it differently: you have disposed of one asset and acquired another, which can trigger Capital Gains Tax.
In this article, we break down how crypto-to-crypto swaps are taxed in the UK, why HMRC treats them this way, and what it means for your tax return. The article also includes practical examples illustrating how HMRC’s rules apply in practice.
Contents
- 1. What Is a Crypto-to-Crypto Swap?
- 2. Why It Counts as a Disposal
- 3. How to Calculate the Gain
- 4. Example: Swapping ETH for SOL
- 5. Example: Partial Disposal and Share Pooling
- 6. Record Keeping and Tools
- Conclusion
1. What Is a Crypto-to-Crypto Swap?
A crypto-to-crypto swap is simply the exchange of one crypto asset for another. This might be swapping Ethereum (ETH) for Solana (SOL) on a centralised exchange or through a decentralised protocol.
Even though no cash is involved, HMRC treats the swap as two separate events:
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You have disposed of the token you gave up.
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You have acquired a new token in its place.
Because the disposal of the first token is a chargeable event for Capital Gains Tax (CGT), this transaction may need to be reported if there is a taxable gain, just like if you had sold the crypto for cash and then immediately bought another asset.
2. Why It Counts as a Disposal
Under UK tax rules, a taxable disposal usually occurs when you cease to have beneficial ownership of an asset. In a crypto-to-crypto swap, this happens the moment you give up one token in exchange for another.
HMRC treats each cryptocurrency as a separate asset, even if both are crypto tokens. This means the swap is not treated as a neutral exchange for tax purposes. Instead, you are treated as:
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Disposing of Token A at its market value in pounds sterling at the time of the swap
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Acquiring Token B as a brand-new asset, also valued in pounds sterling at the same time
This is why swaps create a chargeable event for Capital Gains Tax (CGT), even when no cash is received.
Many investors find this counterintuitive at first, particularly where they have simply moved from one token into another without converting back to pounds. For a broader discussion of why crypto-to-crypto swaps are treated as disposals under UK tax rules, see our article on why crypto swaps are taxed.
3. How to Calculate the Gain
The tax impact of a crypto-to-crypto swap is based on the asset you are disposing of, not the one you are acquiring. In other words, you calculate the gain or loss on Token A at the point you swap it, and treat Token B as a new acquisition.
To calculate your gain on a swap, follow these steps:
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Identify the token being disposed of (Token A)
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Determine the proportion of your pooled cost (see Section 104 pooling) for Token A that is being disposed of
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Find the GBP market value of Token A at the time of the swap
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Subtract the pooled cost from the disposal value to find the gain or loss
The market value of Token B at the time of the swap becomes your acquisition cost going forward. When you eventually dispose of Token B, its gain or loss will be calculated separately, based on this new cost.
This ensures that gains and losses are calculated separately for each cryptoasset disposed of, even if you never receive any cash.
4. Example: Swapping ETH for SOL
The following example shows the basic tax treatment of a crypto-to-crypto swap where the full holding is disposed of.
Tom holds 1 ETH with a pooled cost of £1,200. In March 2025, he swaps it for 50 SOL when ETH is worth £2,000.
This creates a disposal of ETH at market value:
- Disposal value = £2,000
- Cost = £1,200
- Gain = £800
Tom must report the £800 gain on his tax return. The 50 SOL are acquired at a cost of £2,000 for CGT purposes.
This is a relatively straightforward example. In practice, calculating gains on crypto swaps often requires the application of HMRC’s share pooling and matching rules, particularly where there have been part disposals of a token.
5. Example: Partial Disposal and Share Pooling
Sophie owns 5 BTC with a total pooled cost of £75,000 (£15,000 per BTC). She swaps 1 BTC for another token when BTC is worth £30,000.
- Disposal value = £30,000
- Cost of 1 BTC from pool = £15,000
- Gain = £15,000
Her BTC pool now consists of 4 BTC with a remaining cost of £60,000.
The new tokens are acquired at a cost of £30,000 for CGT purposes.
6. Record Keeping and Tools
Tracking your swaps and base costs manually is possible but quickly becomes complex, especially when share pooling is involved. If you’re swapping part of a holding, you need to determine your S104 pool values at the time of each swap. Swapping part of a BTC holding, for example, requires you to understand the average cost of your entire BTC pool and adjust it accordingly.
The complexity increases further if you are transacting regularly, as keeping a reliable record of both disposal and acquisition values whilst also taking into account the same-day and 30-day matching rules becomes extremely difficult without specialist software.
Investors therefore typically use specialist crypto tax software such as Koinly to maintain records and calculate disposals consistently under UK tax rules. These are designed with UK tax rules in mind and can automate much of this process.
Accurate record keeping includes:
- Date and time of each swap
- Tokens disposed of and acquired
- GBP value at the time of disposal
- Source of valuation data
Good record keeping from the outset can significantly reduce future compliance and reporting issues.
Conclusion
Crypto-to-crypto swaps are not tax-free. They are disposals under UK CGT rules, and gains must be calculated at the time of each swap. Even if you never “cashed out”, these transactions are taxable.
This is one of the primary reasons crypto investors can end up with unexpected tax liabilities. Swapping between tokens can create taxable gains without generating any cash to pay the resulting tax bill, which may then require the disposal of further cryptoassets to fund the liability.
If you are still getting familiar with how HMRC taxes crypto more generally, see our Beginner's Guide for an overview of the main rules affecting crypto investors.
If you need help quantifying gains or losses from historic crypto swaps or correcting past reporting, we can help assess your position and advise on the best way to proceed.
