Special Memorandum Account - SMA

Trading on margin involves borrowing cash from your broker to make additional trades. The special memorandum account gets filled if those margin-bought investments start to go up in value. That extra, unrealized value gets accounted for in the SMA as a line of credit.

Probably best to explain this one with an example:

You deposit $10,000 into a trading account. Then you borrow an additional $10,000 on margin. You use the $20,000 to buy 1,000 shares of Flappy Jacks Inc., a maker of premium pancake oil extract. The shares are trading at $20 when you buy them. Within a few weeks, they're up to $25. The value of your stake is up to $25,000...a total unrealized gain of $5,000 (unrealized because it only becomes a real gain if you sell the shares and lock in the profit). Of the $5,000 in paper profits, $2,500 stays in the main account. This amount represents the gain posted using the your original $10,000 cash deposit. The other $2,500, the amount of gain related to your $10,000 margin loan, exists in the SMA.

The SMA largely exists as an accounting tool. The money is treated differently because it was earned on the margin loan, not on the cash you deposited. Once you sell the stock, and square up the margin loan, you can pay back the $10,000 (plus any interest) and transfer that $2,500 SMA amount into actual cash.