What's the Difference Between a Margin Call and a Regulation T Call?

The core difference: when each one is triggered

A Regulation T call is about the initial purchase. Under the Federal Reserve's Regulation T, you can borrow up to 50% of the purchase price of most marginable securities, meaning you must put up at least 50% of your own money. If a trade is executed and the account doesn't have enough equity to cover that 50% initial margin, a Reg T call is issued for the shortfall — this is a one-time check tied to that specific transaction.

A maintenance margin call is about what happens after the position is already open and marginable. FINRA Rule 4210 requires a minimum of 25% equity in a margin account at all times, but that's a regulatory floor, not what most brokers actually enforce — brokers commonly set a higher "house" maintenance requirement, often in the 30% to 40% range, specifically to protect themselves from market risk beyond the regulatory minimum. If the market moves against an open position and account equity drops below that maintenance threshold, the broker issues a maintenance call regardless of what the initial Reg T requirement was when the position was opened.

Side-by-side comparison

What happens if you don't meet either one

• For a Reg T call, brokers typically give a short window (commonly around two business days) to deposit funds or securities; if it's not met, the broker can liquidate the position that caused the shortfall or restrict the account to trading with fully paid-for funds only going forward.
• For a maintenance call, the broker's standard margin agreement generally allows it to liquidate any position in the account, not necessarily the one that caused the call, and can often do so without prior notice to bring equity back above the maintenance threshold.
• Either type of call can result in forced selling at a time and price you don't control, which is the main practical risk of trading on margin at all.