A special account where excess margin generated from a client's margin account is deposited. Also known as "special miscellaneous account".
The purpose of an SMA is to lock in any gains realized in a client's margin account. Consider the situation where stock within a client's margin account realizes a capital gain and creates excess margin. If this excess amount is held in the account and the stock position produces a capital loss at a later date, the client would lose his or her gain entirely.

An SMA can also hold interest and dividend payments from long positions and proceeds from closing out a securities position. Clients can use funds in their SMA to purchase additional securities for their margin account.