GLOSSARY // Risk & Psychology
Maintenance Margin
Maintenance margin is the minimum equity, as a percentage of position value, that a margin account must hold after a position is opened. FINRA sets the regulatory floor at 25% for long stock; brokers typically impose stricter house requirements of 30-40%, and raise them further on volatile or hard-to-borrow names.
The distinction from initial margin matters: Reg T's 50% applies at purchase, maintenance applies every day after. House requirements can also change without much warning — brokers routinely hike maintenance on a single volatile ticker to 75% or even 100%, which can force deleveraging even when the price has not moved.
A trader holds $16,000 of stock against an $8,000 loan at a 25% maintenance requirement. Equity falls below the line when the position drops under $8,000 / 0.75 = $10,666.67 — a 33.3% decline. If the broker raises the house requirement on that ticker to 50%, the trigger jumps to $16,000 — exactly the current position value, so the account sits right at the line and one downtick puts it in a call.
Related terms
Educational only — not financial advice. Definitions simplified for clarity; markets are messier than definitions.