A line of credit created when the market value of securities in a Margin account increases in value. If the SMA balance at the end of the trading day is negative, your account is subject to liquidation.
Your real-time SMA is calculated as follows (whichever is greater):
SMA = ((Prior Day SMA +/- Change in Day’s Cash +/- Today’s Trades Initial Margin Requirements) or (Equity with Loan Value – Reg T Margin))
IBKR enforces Regulation T initial margin requirements (typically 50% for stocks or 100% for nonmarginable securities) at the end of the trading day. Whenever you have a position change on a trading day, we check the balance of your SMA at the end of the US trading day (15:50-17:20 ET), to ensure that it is greater than or equal to zero.