Margin & Mark-to-Market: Settling Every Day

Last lesson we said the clearing house guarantees every futures trade. This lesson is how — and it turns out the magic is mostly bookkeeping discipline. A future doesn’t quietly accumulate one big payoff and reveal it at expiry. Instead, every single day, the exchange tallies up who won and who lost and moves the cash there and then. You can’t run up a secret loss you can’t cover, because the bill arrives nightly. The mechanism is called margin and mark-to-market, and understanding it explains both why futures are so safe for the system and so dangerous for the over-leveraged individual.

Initial margin: the good-faith deposit

Analogy. When you rent a flat, you hand over a security deposit. It isn’t rent and it isn’t the price of the flat — it’s a cushion the landlord can draw on if you trash the place. You get it back if you behave. Initial margin is that deposit, posted to the clearing house before you’re allowed to trade.

Definition. Initial margin is the amount you must deposit in your margin account to open a futures position. The exchange sets it to comfortably cover a bad day’s move on the contract — typically a single-digit percentage of the contract’s notional (face) value. Critically, margin is a performance bond, not a payment for the asset: you control the full notional exposure while posting only the margin. That gearing is the source of futures’ famous leverage (and we’ll quantify it below).

Maintenance margin and the margin call

Analogy. Back to the flat: imagine the lease says your deposit must never fall below a floor. Cause some damage and dip below it, and the landlord demands you top the deposit back up to full — today — or you’re evicted. That floor is the maintenance margin, and the top-up demand is a margin call.

Definition. The maintenance margin is a lower threshold (below initial margin) that your account equity must stay above. Each day, mark-to-market debits your losses; if your equity falls below the maintenance level, the clearing house issues a margin call — a demand to restore your account, usually back up to the initial margin level (not merely back to maintenance). The required top-up is the variation margin you must wire in. Miss the call and the broker liquidates your position to stop the bleeding. The maintenance buffer is what gives the clearing house time to act before your losses exceed your deposit.

Mark-to-market: the daily true-up

Definition. Mark-to-market is the daily ritual at the heart of it all. After the close, the exchange sets an official settlement price. Every position is re-valued at that price, and the day’s gain or loss — the day’s price change times the contract size — is swept in cash into or out of each trader’s margin account. Winners are credited; losers are debited. This variation margin flow happens every trading day, so a position never builds up more than one day’s unsettled loss. That’s the safety valve: the clearing house is never exposed to more than a single day’s move on any account.

Step through it below. The bar is your account equity; the dashed line is initial margin, the orange line is maintenance. Advance day by day and watch a losing streak drag equity toward the floor — when it punches through, a margin call fires and the account is topped back up to the initial level:

Worked example — a full daily ledger

You go long one contract on 100 units of an asset at $100. Initial margin is $6,000; maintenance is $4,500. Here’s the position settled day by day (price moves are per unit; variation = move × 100):

Walk through Day 2: you start at $5,200, lose $1,000 to fall to $4,200, which is below the $4,500 maintenance floor — margin call. You must wire $1,800 to restore equity to the initial $6,000 (not just to $4,500). On Day 3 you gain $600 and sit comfortably at $6,600. Notice the cash actually moved each day — futures P&L isn’t a paper number waiting for expiry; it’s settled cash, nightly.

Leverage: the magnifier that cuts both ways

Now the dangerous, exhilarating part — and the reason people both love and blow up on futures.

Analogy. A crowbar lets a small push move a heavy rock. Leverage lets a small deposit move a large position. Wonderful when the rock goes where you want; it’ll also flatten your foot if it rolls back.

Definition. Leverage is the ratio of the notional you control to the margin you posted. Because you feel gains and losses on the full notional while having tied up only the margin, your percentage return on the margin is multiplied by the leverage factor. Formally, with leverage $L = \text{notional} / \text{margin}$, a small percentage move $r$ in the underlying produces roughly $L \times r$ on your margin.

Worked example — leverage arithmetic

You post $6,000 margin to control $80,000 of notional — leverage $L = 80{,}000 / 6{,}000 \approx 13.3\times$.

• The underlying rises just 2%: notional gain = 2% × $80,000 = $1,600. On your $6,000, that’s a +27% return. A 2% market move became a 27% gain.
• The underlying falls 2%: you lose $1,600 — a −27% hit to your margin, and you’re well on the way to a margin call.
• The underlying falls 7.5%: you lose $6,000 — your entire deposit gone, on a move the asset itself would shrug off.

That asymmetry of feeling — tiny market move, huge account move — is leverage. It’s why a future can lose more than your initial margin: cross past a full wipe-out and you owe more than you put in (which is precisely what margin calls and liquidation are racing to prevent).

Curing a margin call (and what happens if you don’t)

When the call comes, you have three responses:

1. Wire the variation margin — deposit cash to restore equity to the initial level, and your position lives on.
2. Reduce the position — close part of it, shrinking the notional (and thus the required margin) until your remaining equity is sufficient.
3. Do nothing — and the broker will forcibly liquidate your position at the market, crystallising the loss and protecting the clearing house. You don’t get a vote on the timing or the price.

The brutal feature of forced liquidation is that it happens at the worst moment — when the market has already moved hard against you — often locking in the maximum loss. Disciplined futures traders therefore keep a cash buffer well above the minimum, precisely so a normal wobble never forces them out at the bottom.

Why daily settlement makes the system safe

Step back and admire the design. Because every position is trued-up in cash daily:

• No one accumulates a huge unpaid loss — the most you can owe is one day’s move plus your margin buffer, which is exactly the window the maintenance threshold protects.
• The clearing house’s exposure is tiny and short-lived, so its guarantee from lesson 2 is actually credible.
• Defaults are caught early — a trader who can’t meet a small daily call is liquidated long before the loss grows systemic.

The cost of all this safety lands on the individual: the daily cash drain. A hedger who is “right” in the long run can still be forced to fund a string of margin calls along the way if the market zigs before it zags. That cash-flow pain — being right but margin-called into oblivion before you’re vindicated — is the dark side of mark-to-market, and a real reason some hedgers prefer cash-flow-friendly forwards.

Putting it together

A futures account is governed by margin and settled by the clock. Initial margin is a refundable good-faith deposit — a performance bond, not a payment — that lets you control a large notional with a small stake. Every day, mark-to-market re-values your position and sweeps the gain or loss in cash as variation margin. Drop below the maintenance floor and a margin call demands you rebuild to the initial level, or the broker liquidates you. The gearing between notional and margin is leverage, which multiplies both gains and losses and means you can lose more than your deposit. The whole apparatus makes the system bullet-proof while making the individual’s life a daily cash-flow test. Here’s the machine on one card:

One mixed recap before we price these things properly:

Key Takeaways