See how daily marking-to-market moves a futures account's equity, and exactly when it triggers a margin call.
You are long 4 ASX SPI 200 futures, entered at 7,400, A$25 per point. Each evening the position is revalued and cash is settled. If equity drops below the maintenance floor, the account is topped back up to the initial margin.
| Day | Settle | MtM P&L | Equity | Call / top-up |
|---|---|---|---|---|
| 1 | 7494 | +A$9,417 | A$33,417 | — |
| 2 | 7461 | −A$3,306 | A$30,111 | — |
| 3 | 7389 | −A$7,257 | A$22,854 | — |
| 4 | 7362 | −A$2,648 | A$20,206 | — |
| 5 | 7326 | −A$3,619 | A$16,587 | call · +A$7,413 |
| 6 | 7337 | +A$1,128 | A$25,128 | — |
| 7 | 7274 | −A$6,279 | A$18,849 | — |
| 8 | 7190 | −A$8,475 | A$10,374 | call · +A$13,626 |
| 9 | 7091 | −A$9,881 | A$14,119 | call · +A$9,881 |
| 10 | 7130 | +A$3,951 | A$27,951 | — |
Cumulative MtM P&L over 10 days = (Fn − F0) · M · N · (+1, long) = −A$26,969. The daily flows telescope to the total price change times multiplier times contracts; top-ups are financing, not P&L.
The cumulative mark-to-market P&L depends only on the start and end price, yet the number and size of margin calls depends on the path in between. Why does the path matter for a trader even when the final outcome is the same, and how does daily settlement protect the clearing house compared with a forward that settles only at maturity?
Assumption: the settlement path is a seeded random walk for teaching, not a forecast. Daily flow uses the Hull (2022) §2.5 convention, with the top-up restoring equity to the initial margin rather than only to the maintenance floor.