When you enter a futures contract, the futures exchange will state a minimum amount of money that you must deposit into your account. This original deposit of money is called the initial margin. When your contract is liquidated, you will be refunded the initial margin plus or minus any gains or losses that occur over the span of the futures contract. In other words, the amount in your margin account changes daily as the market fluctuates in relation to your futures contract. The minimum-level margin is determined by the futures exchange and is usually 5% to 10% of the futures contract. These predetermined initial margin amounts are continuously under review: at times of high market volatility, initial margin requirements can be raised.
The initial margin is the minimum amount required to enter into a new futures contract, but the maintenance margin is the lowest amount an account can reach before needing to be replenished. For example, if your margin account drops to a certain level because of a series of daily losses, brokers are required to make a margin call and request that you make an additional deposit into your account to bring the margin back up to the initial amount.