Marking a swap to market is a technique for valuing it using current market prices. This is done in order to determine its net value, and hence its profit or loss to a counterparty at a specific point in time. Marking to market can be implemented in different methods, all leading to approximate, not identical, numbers, and being based on the yield curve that will be used to discount its cashflows. Swaps are marked to market using an agreed-upon methodology on a periodic basis (daily, weekly, monthly, or whenever the gain and loss exceeds a specific minimum amount).

This technique is sometimes known as a drop-dead analysis.