Self-Custody vs Exchange Crypto: Does It Change Your UK Tax?

The way you hold your crypto — exchange custody, self-custody hardware wallet, or a multi-sig vault — doesn't change the underlying CGT or income tax treatment. But it does change the practical mechanics of filing, the audit trail you have available, and the kind of mistakes that are easy to make.

The tax is identical

Whether your BTC sits on Coinbase, in a Ledger Nano, or behind a Gnosis Safe, HMRC sees it as your asset. Acquiring it is an acquisition; disposing of it (selling, swapping, spending, gifting) is a disposal. The Section 104 pool, same-day rule, and 30-day bed-and-breakfasting rule all apply identically.

Moving between your own wallets is not a disposal. Sending from Coinbase to a Ledger is exactly the same as moving cash between your two bank accounts — no tax event. The HMRC manual is explicit about this: a transfer "to a different wallet for the same beneficial owner" is not a disposal.

What changes in practice

The audit trail differs dramatically. Exchanges produce annual statements showing every trade with GBP-equivalent values, fees, and timestamps. Coinbase, Kraken, and Binance UK all export CSVs that import cleanly into tax software. The data is complete from the moment you opened the account.

Self-custody wallets have no annual statement. The data lives on-chain, addressable via the public blockchain but only if you remember every address you've ever used. Hardware wallets that rotate addresses (Bitcoin best practice) create dozens of distinct receiving addresses; each one needs to be tracked.

Mixing custody types is where most mistakes happen. A user who buys on Coinbase, withdraws to Ledger, swaps via Uniswap, bridges to Arbitrum, and ends up with three months of activity that isn't in any single statement faces a multi-source reconciliation problem at year-end.

DeFi changes the calculus

Pure self-custody amplifies what HMRC considers a taxable event because DeFi protocols don't ask permission. Wrapping ETH to WETH is — per HMRC's most recent draft guidance — a disposal of ETH and an acquisition of WETH. Staking ETH via Lido produces stETH (a rebasing token, income each rebase). Providing liquidity to a Uniswap V3 pool is a disposal of both deposited assets and an acquisition of the LP position.

Exchange-based users tend to do less of this because exchanges restrict the surface area. Self-custody users do more of it and incur more taxable events without realising.

Cold storage's tax implication

Cold storage — long-term self-custody with no recent activity — is the simplest case. No disposals = no tax events. You only have a tax exposure on acquisition (the original cost basis goes into your pool) and on eventual disposal years later. HMRC has no issue with multi-year holds.

The risk: when you finally do dispose, you need the original cost basis. If the exchange you bought through has shut down (Cred, FTX, Mt. Gox) you may have no statement. The HMRC guidance on missing records expects "reasonable steps" to recover them; failure to produce records doesn't make the gain disappear, it just means HMRC may assume your cost basis is zero.

Keep purchase records. Print them, scan them, store them in two places.

Multi-sig and shared custody

Multi-sig wallets where you have one of several signers are tricky. If you can independently transfer assets, HMRC treats them as yours. If a meaningful threshold of independent parties is required (e.g. a 2-of-3 family multi-sig with two non-resident relatives), the beneficial ownership question is less clear. The HMRC manual at CRYPTO22000 onwards discusses ownership but doesn't resolve every multi-sig case.

For most personal multi-sigs (you + a backup), assume the holdings are yours for tax purposes unless you have specific advice otherwise.

The audit-trail bottom line

The tax treatment is the same; the paperwork isn't. If you mostly use exchanges, your statements ARE most of your records. If you mostly self-custody, you need a tool that reads on-chain history into a consistent ledger — CryptoLens, Koinly, Recap, or equivalent — because there is no statement to download.

The £3,000 annual allowance applies the same way regardless of custody. Same rates (18% / 24%). Same SA108 filing. The only thing that's different is how much work you do to get there.