Market-to-market (MTM) is a method of valuing positions in financial markets by adjusting the value of the position to reflect the current market price of the assets. This is done by calculating the profit or loss of a position as if it were closed out at the current market price, and then crediting or debiting the account accordingly.
MTM is commonly used in the futures and options markets to account for changes in the value of a position due to market movements. It is also used in some other financial markets to value positions and calculate margin requirements.