An earn-out is part of the purchase price paid after closing, contingent on the business meeting agreed targets.
In a sale
An earn-out is fair when the founder stays in a role that influences the result and the buyer cannot influence the metric; one the founder cannot control is better read as a price cut than as part of the price. It bridges a gap between what a founder believes the business is worth and what a buyer will underwrite.
Where it comes up
The Go-To-Market Analysis (GTMA) builds the file a buyer would build on your business, before a buyer does.