Margin — day, overnight, and why the number moves

Margin is the number in futures that beginners read as a price and professionals read as a warning. It is neither the cost of a contract nor a down payment on one: it is a deposit the clearing house holds against the losses your position might run up before it can be closed, and it is recalculated as the market's temperament changes. This page is what the two margin figures you will meet actually are, who sets each one, how far they can move, and what happens on the day you do not have them.

A deposit, not a price

CME Clearing's own words for margins are "performance bonds": "deposits held at CME Clearing." Its education material is blunter still — margin "is not a down payment and you do not own the underlying commodity." There are two levels. Initial margin is what you must have to open a position. Maintenance margin is the smaller amount that must be in the account at all times after that; CME warns that a position "may be liquidated automatically once it drops below the maintenance margin level." Losses are collected in cash every evening (how a futures contract works has that mechanism), so an account slides toward the maintenance line one settlement at a time.

The exchange sets the minimum. Your broker holds the deposit and may ask for more — CME's note that "your broker may be required to collect additional funds" is the polite version; Tradovate's policy says it plainly: "Minimum Initial Margins are set per contract by the exchange" and the firm "reserves the right to set Initial Margins higher than exchange minimum requirements."

Two numbers, fifty times apart

Open a broker's margin table and you will see two figures per contract that look like they belong to different instruments.

The overnight (or position, or maintenance) margin is the exchange's requirement, or the broker's mark-up of it, to carry a contract past the daily close. When the desk's margin figures were last read at its broker, on Aug 27, 2026, that was about $2,858 per Micro E-mini S&P 500 contract and $28,579 for the full E-mini. On October 1, 2026 CME's own page listed the exchange maintenance level at $2,608 for a Micro and $26,076 for the E-mini (December 2026 contract, long side) — so a broker's overnight figure ran about ten percent above the exchange's minimum, which is a common mark-up.

The day (intraday) margin is something else entirely: a discount the broker extends while the market is open and it can watch your account tick by tick. AMP's FAQ draws the line exactly: "The Maintenance Margin is set by the exchange. This is the amount required to carry a contract past the daily close," while "DayTrade Margin is set by" the broker. At the desk's broker the day figure was about $50 per Micro ($500 per E-mini) on the same reading — roughly a fiftieth of the overnight requirement.

The day figure is a convenience, not a measure of risk. The broker offers it because it can liquidate you in seconds; the exchange never sees it. That is why the desk sizes positions from the stop and never from margin — position sizing from the stop has the arithmetic, and the short version is that a $10,000 account could hold two hundred Micros on day margin and lose all of it on a ten-point move.

Why the number moves

CME's clearing house sets margins "to cover 99 percent of the potential price moves" over a set period, "usually one trading day for futures markets." Its current margin model is described the same way: cover "at least 99% of anticipated price changes" over a given liquidation period. When volatility rises, the range of moves that 99% has to cover widens, and the margin rises with it; when markets calm, it falls. CME says "changes are often made when the volatility environment experiences a sustained change" and promises "at least 24 hours' notice."

Run the numbers on the Micro: $2,608 of exchange maintenance divided by $5 a point is about 520 index points of cover — nearly 9% of an index at 6,000. That is the size of day the clearing house was budgeting for in autumn 2026, and it is a direct readout of how violent recent markets had been.

Most changes are undramatic. One August 2024 clearing advisory, issued "as per the normal review of market volatility," raised the E-mini's and Micro's maintenance margins by roughly five percent, effective after the close three days later. The dramatic case is March 2020. By FIA's account the E-mini's initial margin began 2020 at $6,300 per contract, was $6,600 by March 2, and was then raised six times in three weeks to $12,000 by March 23. Clarus Financial Technology's tally of the full-size S&P contract over the same stretch runs from $33,000 on February 26 to $60,000 — an 82% increase — with increases on March 2, 4, 10, 13, 17 and 19. An account that held a position through that month with the margin it had in February was asked, repeatedly, for money it may not have had, at the worst moment to find it.

The day you do not have it

Fall below maintenance and the broker issues a margin call. What a margin call means in futures is narrower than most people expect. Schwab's disclosure: the firm "may liquidate, without contacting you, to meet a margin call," and "you are not entitled to an extension of time on a margin call." Tradovate's policy: "the firm may liquidate the account with or without notification," with a fee for each violation. The liquidation happens at whatever price the market offers at that moment, which in a volatile market is exactly when prices are worst.

This is the fact behind the overnight page: the desk's one overnight hand is gated on whether an account can post the overnight requirement with room to spare, and the gate exists so that a member meets the margin arithmetic here, on a quiet page, rather than at 3 a.m. in a broker's liquidation engine.

Why the figures on this page carry a date

Every margin figure on this site is quoted with the day it was read, and the desk's own clock warns the founder when that reading is more than 45 days old. Quoted bare, "$2,858" reads as a fact about the instrument. It is not. It is a measurement of one broker's requirement on one day, derived from an exchange figure that is itself a rolling estimate of the market's recent violence, and it will be a different number the next time anyone looks. Before trusting any margin figure to the dollar — including these — open the broker's current table.

The short version

Margin is the clearing house's deposit against your losses, set to cover 99% of a day's moves and changed whenever volatility changes. The overnight figure is the exchange's minimum or a little more; the day figure is a broker's courtesy worth about a fiftieth of it, and sizing from it is how accounts die. When volatility spikes the requirement can double inside a month, and a shortfall is met by liquidation at the market's price, without a phone call.

• How a futures contract works, in money terms
• What a backtest can and cannot tell you
• Why one hand on the rack and not ten
• How to read a win rate
• What holding overnight really takes

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