Mark to the Market Law and Legal Definition

Mark to the market is an adjustment in the valuation of a security or a portfolio due to a change in the market price of the security. When an investment is marked to the market, its value is adjusted to reflect the current market price.

For example, margin accounts are marked to the market to ensure current compliance with margin maintenance requirements, and the net asset value of a mutual fund is marked to the market so shareholders can see the daily value of the portfolio. If that value falls below the minimum specified, you get a margin call and must add assets to your account to return it to the required level.