MEV (Maximal Extractable Value)
Also known as: maximal extractable value, miner extractable value
Value that validators or bots can extract by reordering or inserting transactions in a block; relevant for traders facing slippage and failed swaps.
Definition
Maximal Extractable Value (MEV) is the profit that block producers or specialised bots can capture by choosing the order, inclusion or exclusion of transactions — for example front-running a large DEX swap. For most taxpayers MEV is background, but it can cause slippage, failed transactions with wasted gas, and unexpected execution prices, all of which affect the proceeds, base cost and fees you must record accurately.
Example
A bot front-runs your DEX swap, so you receive less than expected; the actual proceeds and gas (including a failed attempt) are what you record.