Maintenance Margin is the amount of funds which must be maintained in order to continue holding a position. In the U.S., the rules of the listing exchanges define the maintenance margin requirements on security transactions subject to SEC approval. The exchange minimum maintenance margin requirement for long stock positions is currently set at 25% although brokers can add any amount of a "house margin" requirement in excess of that, particularly where the security is considered low-priced or subject to volatile price changes. The exchange minimum maintenance margin requirement for short stock positions is currently set at 30%.