Slashing is a penalty a proof-of-stake network imposes on a validator that breaks its rules, by destroying part of the validator's staked balance. Signing two conflicting blocks is the usual trigger; on some chains extended downtime is slashed as well. On many delegated chains, the delegators to that validator lose the same proportion of their stake.
The protocol detects the offence from the validator's own signatures, so there is no accusation and no appeal: the evidence is on-chain and the penalty is applied by the code. On Ethereum a slashed validator loses an initial amount, is forced to exit, and loses more depending on how many other validators were slashed around the same time. Cosmos chains burn a percentage of the bonded stake, larger for double signing than for downtime, and jail the validator. On many delegated chains the burn is applied pro rata across every delegation to the validator, so a delegator who did nothing wrong loses tokens because of the operator they chose.
Slashing is not a theft, a hack or a rug pull. The tokens are not taken by a counterparty; the protocol burns them. It is also not a sale: no proceeds come back and no exchange takes place. The tokens cease to exist, along with whatever you paid for them. Missed rewards from downtime or jailing are a separate matter; they are income you never received, not a loss of anything you held.
The tax character of a slashing loss is not settled by published guidance. What is settled is what it is not. It is not a sale or exchange, because nothing was received for the units, so there are no proceeds to report. It is not a theft loss, because no one took the property. And it is not income foregone: only staked units you already held, with basis already attached, are affected. Whether the amount can be deducted, in which year and under which limits depends on how the loss is characterised, and a return that claims a deduction needs to state its ground.
What the accounting needs is clear regardless of character. The slashed quantity, the date and the lots it came out of must be recorded, and the basis of those units removed from the book. Left in place, that basis attaches to units that no longer exist and is eventually claimed against a disposal of other units, understating gain. For a delegator, the loss is the delegator's own share of the burn, taken from the delegator's own lots; the validator's loss is the validator's.
The units that remain are unchanged: same basis per unit, same holding period. Slashing reduces the quantity, not the per-unit figures. Where the validator was forced to exit, the returned balance is principal less the penalty plus any final rewards, and the three parts are separated in the record rather than treated as one receipt.
A burn that no transaction records. Slashing changes a balance without a transfer, so wallet imports never see it. The book carries the full pre-slash quantity and basis, and the first sign is a negative balance when the reduced stake is later withdrawn and sold, or, worse, no sign at all: the phantom units and their basis are quietly consumed by later disposals and the gain on those is understated by the value of tokens that were burned years earlier.
Read our Are Crypto Staking Rewards Taxed? Yes, Here's How in 2026
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