Maintenance Margin
The minimum equity level a futures account must maintain; falling below triggers a margin call demanding top-up to initial margin.
Maintenance margin is the lower boundary of acceptable equity in a futures margin account. While initial margin is required to open a trade, maintenance margin is the floor that must be maintained while the position is open.
When daily mark-to-market losses push account equity below the maintenance level, the broker issues a margin call. The trader must deposit enough to bring the account back to initial margin — not just maintenance — by the next session's open. Failure to meet the call results in forced liquidation.
Maintenance margin is typically ~90% of initial margin for most CME products — the clearinghouse usually sets initial at about 1.1× maintenance (e.g. ES $15,840 initial vs $14,400 maintenance). These figures are set by the exchange and change with volatility, so always check the current spec.
On the desk
ES initial margin = $15,840; maintenance margin = $14,400. A trader enters long with $16,000. Three consecutive down days lose $1,700 — equity falls to $14,300, below maintenance. The broker calls for $1,540 to restore the $15,840 initial level.