1, A demand from a clearinghouse to a clearing member, or from a brokerage firm to a customer, to bring margin deposits up to a minimum level required to support the positions held. This can be done by either depositing more funds or offsetting some or all of the positions held.

2, A demand for additional funds by a clearing house, broker, dealer, bank or another financial institution from a client to provide sufficient minimum collateral against positions held. A client that does not produce the required margin call runs the risk of having his positions closed either in part or in full by the dealer as per his discretion for insufficient funds.