Uniswap Tax UK 2026: How Every Swap Becomes a Disposal

Uniswap is where a lot of UK crypto users end up as soon as they leave the beaten path of centralised exchanges. It's non-custodial, permissionless, and — as far as HMRC is concerned — full of taxable disposals people are quietly ignoring. Here's the honest tax picture for a UK Uniswap user in the 2026/27 tax year.

The core rule

Every token-to-token swap on Uniswap is a disposal of the token you're paying with, at the market value of the token you're receiving. HMRC's CG12100 is unambiguous: swapping ETH for USDC is a disposal of ETH, even though no fiat changed hands.

The market value of the incoming token at the moment of the swap is your proceeds. Your cost basis for the ETH you spent comes from Section 104 pooling of your prior ETH acquisitions. The difference is your gain (or loss), and it feeds into your Capital Gains Tax position for the year.

Practical implication for high-frequency users

If you did 400 Uniswap swaps in the tax year, that's 400 disposals — not 400 "trades that ended flat because I ended up with the same USD value". Even if your overall wallet is up or down 5% for the year, every intermediate swap crystallises a discrete gain or loss.

This is where CryptoLens does the heavy lifting. Paste your wallet address, we walk every swap, price both legs against GBP at the block timestamp using CoinGecko historical data, and produce a per-disposal ledger with the correct S104 cost basis applied.

Gas fees are deductible

The ETH you spend on gas for a Uniswap swap is an allowable transaction cost — it reduces the disposal proceeds on the outgoing swap and adds to the cost basis of the incoming acquisition. HMRC CG15250. This isn't small change: at 30 gwei on a busy day, a Uniswap V3 swap can burn £5-15 in gas. Across a year of activity, thousands.

Some Uniswap wrappers (Universal Router, aggregator routes through 1inch/Cowswap) split gas across multiple sub-legs. Pull the raw tx receipt from Etherscan and take the total gas cost — that's what HMRC considers your incidental expense of disposal.

Liquidity provision (Uniswap V2, V3, V4)

This is where UK guidance gets uncertain. HMRC hasn't published clear crypto-specific guidance on AMM LP entries and exits. The prudent readings:

- **Entering a pool** is treated by many practitioners as a disposal of the two tokens you deposited, followed by an acquisition of the LP receipt token (V2) or the position NFT (V3/V4) at their combined market value. - **Earning fees** is treated as income at the point of accrual, at the market value on the date accrued. - **Exiting a pool** disposes of the LP/NFT, acquires whichever tokens you withdraw, and generates a further gain/loss between the disposal value and the reacquisition value.

CryptoLens treats LP entries conservatively by default (HMRC CRYPTO22600 "no disposal" reading) — flip the DeFi treatment toggle in Account Settings to Aggressive if your accountant prefers the crystallisation approach.

Wrapped tokens (WETH, wstETH, stETH)

Wrapping ETH into WETH to interact with Uniswap is not a disposal — HMRC's guidance on tokenised claims is that a wrapper representing the same underlying, redeemable 1:1, doesn't crystallise. But wrapping ETH into stETH (Lido) *is* a disposal in the conservative reading, because you're now exposed to Lido's smart-contract risk plus a variable staking-yield component. CryptoLens defaults to conservative; you can override per-token in Account Settings.

The self-report burden

CARF (Crypto-Asset Reporting Framework) took effect 1 January 2026. Uniswap, being a non-custodial DEX, doesn't sit inside CARF's reporter list — but every on-chain interaction is publicly observable to anyone who wants to look, including HMRC. Under-reporting a year of Uniswap activity is much more visible than under-reporting a year of centralised-exchange activity, because the CEX might quietly not report; the blockchain always does.

How to file cleanly

For the 2026/27 tax year (deadline 31 January 2028):

1. Scan every wallet address you used with CryptoLens — 29 chains supported. 2. Verify the transaction list matches your Etherscan view (spot-check any tx with unusual gas or complex Router hops). 3. Open the /tax page — every Uniswap swap is now one line in the Section 104 disposal ledger. Filter by token to sanity-check. 4. Export the SA108-format PDF plus the full CSV. 5. Keep both for six years after the filing deadline.

The point of the exercise isn't to pay HMRC more — it's to have defensible arithmetic if they ever ask. Uniswap activity is the single most common trigger for "how did you arrive at these numbers?" enquiries, precisely because most people underestimate the disposal count by 10-50x.