Uniswap Tax UK: DEX Swaps, LP Tokens and HMRC Capital Gains

Uniswap is the largest decentralised exchange in the world, and the way HMRC taxes its activity is significantly more aggressive than most UK retail users realise. Every swap is a taxable disposal at the GBP price the moment the transaction confirms — even if you are just rotating stablecoins, even if no GBP ever leaves your wallet.

Swaps are taxable disposals

When you swap WETH for USDC on Uniswap, HMRC treats that as a disposal of WETH at the GBP value of the USDC you received, plus a fresh acquisition of USDC at the same value. You realise a gain or loss on the WETH leg against your Section 104 pool, and the USDC enters your USDC pool at its acquisition cost.

USDC ↔ USDT swaps are still disposals. So are ETH ↔ WETH wraps and unwraps (HMRC has not formally ruled on this, but the conservative default is to treat them as different tokens). DAI → LUSD swaps. Every leg.

LP tokens: two events per position

Adding liquidity to a Uniswap v2 pair (or wrapping a position in v3) generally counts as a disposal of the two underlying tokens for the LP token, then a fresh acquisition of the LP token at the same GBP value. When you remove liquidity, the LP token is disposed and you re-acquire the underlying assets.

This means a single LP cycle can generate four taxable events: deposit (2 disposals), withdraw (1 disposal of the LP, 2 acquisitions). Fees collected during the position are also taxable income at the GBP value on the day they are claimed.

Uniswap v3 concentrated liquidity

v3 positions are NFTs, not fungible LP tokens. Each position has its own contract address and ID. HMRC treats each minted v3 position as a separate asset for cost-basis purposes — when you "increase liquidity" on the same NFT, the conservative position is to treat it as adding to the same asset (no new disposal), but every "decrease liquidity" or "collect fees" call is a partial disposal that must be valued in GBP at the block timestamp.

MEV and failed transactions

Failed Uniswap transactions still cost gas. The gas fee on a failed swap is generally an allowable cost against your overall gains for the year, but only if you have records linking it to disposal activity. MEV-protected swaps (1inch Fusion, CowSwap, MEV Blocker) settle the same way for tax — the fact that the route differs makes no difference, only the in/out tokens and timestamps.

Reconstructing it manually is impractical

A typical active Uniswap user generates 200-500 swaps per year across mainnet, Arbitrum, Base and Optimism. Each one needs a GBP price at execution, the corresponding pool entry, fee deduction, and a Section 104 update for both the in and out tokens. Doing that by hand against historical price oracles is the largest reason UK Uniswap users miss the 31 January Self Assessment deadline.

CryptoLens scans every connected EVM wallet, prices every Uniswap swap (v2, v3, and the new v4 hooks) at GBP at block time, and produces an HMRC-ready CGT summary in seconds.