Explain what margin and a clearing house do
The idea
A central counterparty interposes itself between buyer and seller, becoming the buyer to every seller and the seller to every buyer, so neither party is directly exposed to the other's solvency, being exposed to the clearing house instead, which relies on margin and a default fund. It protects itself with initial margin, posted at the outset to cover a plausible one-day move, and variation margin, which settles the day's gain or loss in cash. If the account falls below the maintenance level, a margin call restores it to the initial level under the usual convention - not to the maintenance level, which is a detail that trips up many candidates.
Formulas
Margin account balance and margin call
B₁ = B₀ + G and M = I − B₁
- B₁
- the account balance after the day
- B₀
- the balance before
- G
- the day's gain, or minus the day's loss
- M
- the margin call, the cash to deposit
- I
- the initial margin the account is topped up to
A call is made when the balance falls below maintenance margin, and it restores the account to initial margin, not to maintenance.
A practice question
What is the function of initial margin on a futures position?
- It is the premium paid for the contractWhy not: Futures have no premium; the trader's margin remains their own money and is returned when the position closes.
- It is a good-faith deposit covering a plausible adverse move - correct
- It is the final settlement of the contractWhy not: Settlement happens daily through variation margin and finally at expiry. Initial margin is a deposit held throughout.
Initial margin is a good-faith deposit you put up when you open a futures position. It is not a fee or a premium. It is your own money, set aside to cover a likely bad day's loss, and it is returned when you close the position, adjusted for your gains and losses. Rule: Initial margin = a deposit sized to cover a plausible adverse move. Daily gains and losses are settled separately through variation margin, and the contract is finally settled at expiry.
A harder one
Tom Becker buys 5 futures contracts. The initial margin is $4,000 per contract and the maintenance margin is $3,000 per contract. He deposits the initial margin on day 0. The position loses $3,000 on day 1 and a further $4,200 on day 2, with no other deposits or withdrawals. Under the usual convention, how much must Tom deposit to meet the margin call after day 2?
- $7,200 - correct
- $2,200Why not: The deposit has only restored the account to the maintenance level. The usual convention requires a margin call to restore the account to the initial margin level.
- $4,200Why not: This is just the day 2 loss. The call is sized by the shortfall against the initial margin level of the whole account, which includes the day 1 loss as well.
Deposit needed = Initial margin level - Current balance, once the balance falls below maintenance. Total initial margin = 5 x 4,000 = $20,000. Total maintenance margin = 5 x 3,000 = $15,000. After day 1: 20,000 - 3,000 = $17,000, above $15,000, so no call. After day 2: 17,000 - 4,200 = $12,800, below $15,000, so a call is made. Restore to initial margin: 20,000 - 12,800 = $7,200. Topping up only to maintenance would be $2,200. The $4,200 answer covers only day 2's loss.
The hardest tier
How does a central counterparty change the credit structure of a derivatives market?
- It replaces many bilateral exposures with one exposure to the clearing house - correct
- It removes credit risk because trades are netted down to zeroWhy not: Netting reduces gross exposure but the risk concentrates in the clearing house, which is why its own margin model matters so much.
- It shifts all credit exposure onto the party with the larger positionWhy not: Exposure is to the clearing house, not to the larger party. Participants still default, and the structure changes who bears the consequences.
A central counterparty (CCP), or clearing house, steps in between buyer and seller, so each trader faces the CCP instead of many different parties. Many exposures become one exposure, to a single body that takes margin (cash deposits) and holds its own capital. Example: a dealer that owed money to ten counterparties now owes the net amount to the CCP alone. Credit risk is not removed. It is concentrated and backed by collateral, which is why the CCP's own risk controls matter so much.
In the app: 9 practice questions on this outcome, a narrated walkthrough with diagrams, spaced review that brings it back before you forget it.
Take the free diagnostic →