Futures are not paid for upfront like spot assets. Instead, both parties post initial margin — a performance bond, typically 3–12% of notional — into a margin account. Each day the exchange marks to market: gains are credited, losses debited, and the balance is reset to the initial level if it drifts.

If the balance falls below the maintenance margin (often ~75% of initial), a margin call triggers. The trader must top up to the initial level by the next session or the broker liquidates the position.

Initial margin: posted to open the trade
Maintenance margin: floor before a call
Variation margin: daily cash flow of gains/losses
Liquidation: forced close if the call is unmet

Concept	Typical Level	Trigger
Initial margin	5% of notional	Open position
Maintenance margin	3.75% of notional	Balance floor
Margin call	Top up to 5%	Balance < 3.75%