The agreed normal level of working capital the business must have at closing; any shortfall or excess adjusts the price.
In a sale
The working capital peg is one of the terms founders most often meet too late. If the business is delivered at closing with less working capital than the peg, the price comes down; with more, it goes up. Where the peg is set is negotiated, and it is best settled while several buyers are still at the table.
Where it comes up
The Go-To-Market Analysis (GTMA) builds the file a buyer would build on your business, before a buyer does.