when a customer opens a margin account up to 50 of the purchase price of the first stock in the account can be borrowed by the customer in accordance with regulation t of the federal reserve board individual brokerage firms have the discretion to increase this percentage 
after a stock is purchased on margin the financial industry regulatory authority finra imposes further requirements on margin accounts one requires that a brokerage hold at least 25 of the market value of the securities purchased on margin 2 the brokerage firm may set a higher minimum the minimum deposit may be up to 50 but some brokerages set a higher amount 2that number effectively becomes the house requirement for a deposit when a house call is issued the account holder must meet the margin maintenance requirement within a stated period fidelity investments for example has a margin maintenance requirement that ranges from 30 to 100 and its house call allows an account holder five business days to sell margin eligible securities or deposit cash or margin eligible securities but fidelity may cover the call at any time portfolio margin accounts follow a different set of requirements after that the firm will start liquidating securities 3 charles schwab has a maintenance requirement that is usually 30 so it can vary with the security but house calls are due immediately by the firm 4