The cash or securities an investor must deposit in his account as collateral before writing options. Margin requirements vary by option type. Margin requirements are established by the Federal Reserve Board in Regulation T; individual brokers may impose additional requirements. Brokers require investors to deposit margin funds because they may be needed to buy or sell underlying stocks if the options are exercised. They may also be needed to close losing positions.

Margin requirements for options trading are different from margin requirements for trading stocks or futures. Also, some options trading strategies have no margin requirement. This is because the underlying stock can be used as collateral. Neither covered calls nor covered puts have a margin requirement, for example.