If you have ever lent crypto on Aave, Compound, Morpho, Spark or any other DeFi lending protocol, your UK tax position may be far less settled than you think. The question of whether entering and exiting a lending position triggers Capital Gains Tax is one of the most consequential grey areas in the HMRC cryptoasset framework, and the answer can change your tax bill by thousands of pounds.
This guide explains why this matters, how the two competing interpretations work, what HMRC has said and not said, and how to position your records and decisions while the issue remains unresolved.
Why DeFi lending is different from buying and selling
Most UK crypto investors understand the basic disposal rules. Selling ETH for GBP, swapping BTC for USDT, spending crypto on a purchase, or gifting tokens to a non-spouse all create disposals that trigger Capital Gains Tax. The mechanics are well-established and HMRC guidance is reasonably clear.
DeFi lending breaks this clean model. When you deposit USDC into Aave you receive aUSDC in return. When you redeem your position, you give back aUSDC and receive USDC. On the surface this looks like a token swap, which should be a disposal. But economically, you never really gave up your USDC, the protocol simply represented your claim as a different token while you held the position.
This is where the concept of beneficial ownership becomes decisive.
Beneficial ownership: the single concept that decides everything
In English law, beneficial ownership is the right to enjoy the economic benefits of an asset, including the right to dispose of it, regardless of who holds legal title. The question HMRC has flagged but never directly answered is whether depositing crypto into a DeFi lending protocol transfers beneficial ownership of those tokens to the protocol, or whether the user retains it throughout.
The answer determines two competing tax outcomes:
Interpretation A: beneficial ownership does not transfer. Under this view, the user is treated as keeping their original tokens economically, and the aTokens or cTokens received are simply a receipt or record of the position. Entering and exiting the loan is not a taxable event. The only taxable element is the interest or yield received, which is treated as miscellaneous income subject to Income Tax.
Interpretation B: beneficial ownership transfers to the protocol. Under this view, depositing tokens into the protocol is a disposal at market value. Receiving the original asset back when you withdraw is an acquisition at the then-current market value. Every entry and exit triggers Capital Gains Tax, calculated against your share-pool cost basis. The yield is still taxable, but the timing and characterisation of the underlying token movements changes completely.
The same Aave position, under the same dates, with the same numbers, can produce a £0 CGT bill under Interpretation A and a £4,000 CGT bill under Interpretation B.
Why HMRC's silence is itself the problem
HMRC's Cryptoassets Manual acknowledges that beneficial ownership is the relevant test but explicitly declines to give a definitive answer for DeFi lending. The manual notes that the answer depends on the specific terms of each protocol, the smart contract design, and whether the lender retains the right to recall the asset or substitute equivalent tokens.
In practice this means:
every major DeFi protocol must be analysed individually, with reference to its specific smart contract logic and terms;
different protocols can produce different outcomes, even when economically they offer the same product;
professional advisers in the UK currently disagree on how to treat the most popular protocols, with reputable Big Four firms taking different positions across client engagements;
HMRC retains the right to challenge any interpretation in audit, and the courts have not yet ruled on a leading DeFi lending case.
The silence is structural, not accidental. HMRC waits for the regulatory perimeter under the upcoming FCA cryptoasset regime to clarify the legal nature of these products before committing to a definitive tax treatment.
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The four practical scenarios most affected
The beneficial ownership ambiguity hits some user profiles much harder than others.
Active DeFi user with frequent positions
Someone moving capital between Aave, Compound, Morpho and Spark to chase yield can have dozens of entries and exits in a single tax year. Under Interpretation B, each one is a disposal with a fresh cost basis calculation. The reporting burden alone, before any tax owed, can be substantial.
Long-term holder using DeFi for passive yield
Someone who deposited ETH on Aave in 2022 and finally exits in 2026 faces a single large disposal at exit under Interpretation B. The capital gain crystallised could be substantial if ETH appreciated during the period, with the £3,000 annual exempt amount offering minimal protection.
Liquidity providers and yield farmers
Adding liquidity to a Curve or Uniswap pool and receiving LP tokens raises the same beneficial ownership question, but with additional layers: impermanent loss, multiple underlying tokens, and reward tokens with their own characterisation issues.
Cross-platform users straddling lending and staking
When the same protocol offers both lending and staking, the beneficial ownership analysis may differ between the two services, even though the user experience is nearly identical. This creates real risk of inconsistent declaration.
Build your records assuming Interpretation B until proven otherwise
Faced with this uncertainty, the conservative and professional approach is to maintain records that allow you to calculate your position under either interpretation. If HMRC eventually rules in your favour, you can revise. If they rule against you, you already have the underlying data to declare correctly.
For each DeFi lending interaction you should capture:
the date, time and exact GBP value of each deposit and withdrawal;
the smart contract address of the protocol and the version interacted with;
the underlying asset deposited and the receipt token received (and vice versa);
all interest or yield received, with GBP value at the time of receipt;
any protocol-specific events such as rebases, liquidations or migrations;
your wallet address and the transaction hashes on-chain for verification.
This level of record-keeping is the same level you would need anyway under CARF reporting starting from 1 January 2026, so it is not wasted work, it is forward compliance.
How to take a defensible position now
If you have existing DeFi lending activity that you have not yet declared, or are about to declare for the current tax year, you have three realistic paths.
Path 1: declare under the more conservative interpretation
Treat every entry and exit as a disposal and pay the resulting CGT. This is the safest position in audit but may overpay tax if HMRC eventually clarifies in favour of the lender-friendly view.
Path 2: declare under the lender-friendly interpretation with full disclosure
Treat only the yield as taxable, do not treat entries and exits as disposals, and disclose your position transparently in the white space of your Self Assessment return. HMRC has the data to challenge you, but you have made your position visible, which materially reduces penalty exposure if challenged.
Path 3: get a written opinion before filing
For positions above roughly £25,000 in lending exposure, a written opinion from a Big Four firm or specialist crypto tax practice typically costs between £1,500 and £5,000, and gives you a defensible position to point to in any future enquiry. This is overkill for small positions, but appropriate for serious DeFi participants.
What you should not do is omit the activity from your return entirely. From 1 January 2026, the platforms know what you did. From 31 May 2027, HMRC will know what the platforms know. The window where non-disclosure was a low-risk strategy has closed.
Why this matters more in the CARF era
Since 1 January 2026, UK cryptoasset service providers must collect detailed user and transaction data under the Crypto-Asset Reporting Framework. The first reports reach HMRC in 2027 covering 2026 activity. For DeFi specifically, the reporting reach is still being defined, but the centralised on-ramps and off-ramps you used to enter DeFi positions are already in scope.
This means HMRC will know that you moved funds into a DeFi protocol, even if they cannot directly see the protocol-level mechanics. If your Self Assessment does not reflect a credible position on those activities, the questions will follow.
The investors who will navigate this transition cleanly are the ones who chose their interpretation deliberately, documented it properly, and made it visible to HMRC. The investors who will struggle are the ones who hoped the question would resolve itself.
How Finbooks helps you take control of your DeFi position
The beneficial ownership question is one HMRC will eventually have to answer, but until they do, the burden of building a defensible position sits with you. The hardest part is rarely the legal analysis. It is reconstructing what actually happened across multiple protocols, chains, wallets and tax years, in a format that is consistent, auditable and ready to support whichever interpretation you adopt.
Finbooks brings that work into one place. You can connect your wallets, lending protocols and exchanges, import full transaction histories, classify deposits, withdrawals and yields, and prepare tax reports that you can use to file directly, share with your accountant, or attach to a disclosure if past years need correcting.
Finbooks does not replace specialist tax advice on a contested area like DeFi lending, and we will not pretend that any software resolves a question HMRC itself has left open. What it does give you is clean, organised, audit-ready data, which is the single most valuable asset you can hold when the regulator finally moves.
Create a free account now: start by getting your DeFi lending records in order. The longer you wait, the harder the reconstruction becomes, and the less freedom you have to choose your interpretation.
