A system and method for trading financial instruments from a master account having a plurality of sub-accounts. A user defines an account group, which includes a plurality of sub-accounts, and the user selects an allocation model for the account group from a group of allocation models. After executing an order of financial instruments for the account group, the order is allocated to the sub-accounts using the allocation model. Prior to executing the order, a financial capability of the account group to execute the order using a primary allocation model is evaluated, and a secondary allocation model is used if the order cannot be allocated using the primary allocation model. The financial capability of the account group may be evaluated in real-time, and a partially executed order may also be allocated to the sub-accounts in real-time. Upon the execution of the order being completed, the order is reallocated to the sub-accounts using the selected allocation model.