DeFi liquidation bonus vs borrower penalty

A DeFi liquidation bonus is the extra collateral transferred when someone repays an eligible borrower's debt. That extra collateral is a penalty to the borrower. A protocol may retain a share, so the borrower's penalty can exceed the liquidator's bonus. Neither percentage establishes liquidator profit: gas, funding costs and the amount received when selling collateral still matter.

The useful question is therefore where each unit went. Separate the debt extinguished, the borrower's total collateral reduction, the liquidator's receipt and any protocol allocation. This guide follows a collateral-for-debt model using a deliberately hypothetical partial liquidation. Other liquidation designs require their own transfer map.

Follow the transfer before comparing rates

In Aave V3's documented model, a position becomes eligible for liquidation when its health factor falls below 1. An external liquidator repays debt and receives collateral with a bonus. Eligibility and the size of the bonus answer different questions: one permits the event; the other helps determine the exchange of value.

The Aave V3 Origin liquidation calculation provides a concrete implementation of a split. It calculates collateral corresponding to the debt, applies the liquidation bonus, derives the bonus portion and takes the configured protocol fee from that portion. The liquidator receives the remainder. This source review describes the repository on 28 October 2026, rather than verifying a particular deployed market or historical event.

That ordering matters. A protocol fee equal to 10% of the bonus is different from an additional charge equal to 10% of all collateral seized. Applying the percentage to the wrong base can make a modest allocation appear enormous.

For centralized products, a liquidation charge can instead be a separately booked settlement item. The liquidation-fee ledger explains that accounting. Here, the penalty is embedded in an exchange: more collateral value leaves the borrower than the debt value removed.

Reconcile a partial liquidation at one price snapshot

Assume a fictional borrower has 4 units of collateral token C, valued at $2,500 each, and 8,000 units of debt token D, valued at $1 each. The position is eligible for liquidation, and its rules permit the partial repayment below. These are invented assets, prices and parameters, not current market quotations or an Aave reserve configuration.

Use a 5% gross collateral bonus and a protocol share equal to 10% of that bonus. The liquidator repays 4,000 D. Assume sufficient collateral, underlying-token delivery to the liquidator, no interest accrual during the snapshot and no rounding difference at the displayed precision.

The collateral equivalent of the repaid debt is 1.6 C: $4,000 divided by $2,500. The 5% bonus adds 0.08 C, worth $200. Total collateral removed from the borrower is therefore 1.68 C, worth $4,200.

The protocol keeps 10% of 0.08 C, which is 0.008 C, worth $20. The liquidator receives the remaining 1.672 C, worth $4,180 at the same valuation price.

The native transfer check is 1.680 C = 1.672 C + 0.008 C. The value check is $4,200 = $4,000 + $180 + $20: debt value extinguished, liquidator uplift and protocol allocation. These are alternative decompositions of the same event, so the intermediate rows must not all be added together.

The borrower now has 2.32 C worth $5,800 and debt of 4,000 D worth $4,000. At unchanged prices, collateral minus debt falls from $2,000 to $1,800. The $200 decline equals the gross penalty.

The borrower did not lose $4,200 of net equity in this snapshot, because $4,000 of debt disappeared too. Nor should the $20 protocol allocation be added again to the $200 penalty: it is already inside the extra collateral removed. This local collateral-minus-debt calculation excludes other wallet assets and whatever the borrower originally did with the loan proceeds.

Give every percentage a denominator

Several apparently conflicting rates can all describe that same transfer accurately.

A 5% bonus on the repayment amount therefore does not imply a 5% discount measured against the gross collateral value. Multiplying $4,200 by 5% would produce $210, which is not the $200 excess in this example.

Before comparing two dashboards, write down whether their rate means gross borrower penalty, liquidator allocation after the protocol share, or a discount against collateral value. Then record its base and asset. Even identical displayed percentages can describe different economic quantities.

The collateral-haircut valuation guide addresses another percentage with a different job: how collateral value is recognized for borrowing capacity. A valuation haircut does not establish how much collateral a liquidator receives.

Convert the liquidator's receipt into an actual result

The $180 liquidator uplift above is a valuation difference. It becomes a cash result only after accounting for acquiring the repayment asset, disposing of collateral and paying execution costs.

Continue the hypothetical example. Suppose the liquidator sells all 1.672 C and receives 4,150 D after the selling route's trading fees. The route realizes $30 less than the $4,180 oracle valuation. Assume D remains worth $1 and repayment funding creates a separate $8 charge. Repayment, liquidation and sale occur within one successful, sender-paid Ethereum mainnet transaction; its total receipt shows 200,000 gas used and an effective gas price of 30 gwei.

Assume the liquidator has enough additional D and ETH to cover charges and any sale shortfall. That funding buffer lets the loss case below settle successfully too; an atomic operation without sufficient repayment resources would instead revert.

The gas fee is 0.006 ETH. At an explicitly assumed reporting price of $3,000 per ETH, that costs $18. Ethereum's gas documentation describes the underlying units-used and gas-price calculation; the numbers here are invented. Separate transactions would have their own charges.

The same result can be checked from the valuation uplift: $180 − $30 − $8 − $18 = $124. Because the sale proceeds already include route trading fees, subtracting those fees again would understate the result.

Now change only net sale proceeds to $3,990. The result becomes $3,990 − $4,000 − $8 − $18 = −$36. The liquidation still transferred a positive collateral bonus at the protocol valuation, but the completed operation lost money. Neither scenario forecasts a liquidator's return.

Keep gas in ETH in the underlying ledger before converting it for comparison. The failed-swap gas guide explains how included failures, approvals and replacement transactions affect the actual bill. A failed included attempt may add expense without producing any collateral receipt.

Resolve the cases that break a simple spreadsheet

Requested repayment differs from actual repayment. Liquidation eligibility does not establish that an arbitrary amount can be covered. Position limits, collateral availability and the active implementation can constrain execution. The reviewed Aave V3 Origin calculation reduces the debt amount needed when available collateral is insufficient. Use the executed amount when reconstructing a real event.

The interface shows a receipt token. Aave V3's Pool documentation allows liquidators to receive aTokens instead of underlying collateral. Receiving a tokenized claim and receiving spendable underlying are different observations. The lending receipt-token accounting guide explains why token identity, balance and redemption evidence belong in separate fields.

A rounded estimate misses the contract result. Integer asset units and rounding directions matter at small amounts. The repository's 3.7 rounding note documents distinct floor and ceiling choices for the collateral and protocol split. Use the implementation active at the event's block for exact reconciliation; a decimal spreadsheet is only an estimate until its smallest-unit arithmetic matches.

A price move gets called a penalty. The worked borrower check holds prices constant. A before snapshot at one collateral price and an after snapshot at another mixes liquidation transfers with market revaluation. Preserve both native quantities first, then value them under an explicit comparison policy.

The position remains open. A partial liquidation leaves collateral and debt. Reconcile remaining interest-bearing balances and risk status rather than marking the account closed because one event succeeded. Do not assume that an advertised maximum liquidation fraction was actually executed or that every successful partial liquidation restored the position to health.

Close the event with evidence from both sides

Start with chain ID, contract addresses, borrower, transaction hash and block. Retrieve the successful receipt and liquidation records, then establish the relevant debt and collateral balances immediately around execution. A transaction may contain several operations, so an account-wide balance difference is not automatically the liquidation amount.

In the reviewed Aave V3 Origin source, the collateral amount emitted in LiquidationCall is the liquidator allocation. The protocol fee moves separately to the treasury through an aToken transfer. Reading the event's collateral field alone as the borrower's total reduction would omit that allocation.

Use this worksheet to make the conclusion reproducible:

When the split does not reconcile, retain the difference as unresolved. Check token units, receipt-token movements, interest accrual, additional operations and rounding before inventing an extra fee.

A completed record should let another reader reproduce three numbers: the borrower's gross penalty, the protocol's share and the liquidator's result after costs. Once those reconcile separately, a displayed “liquidation bonus” becomes a traceable transfer instead of an assumed profit.