1. A computer-implemented method of reducing risk in foreign exchange payment-based transactions between financial market participants, wherein payment is made from an account holder to a counterparty using a payment bank system operated by a payment bank, the method comprising the steps of: generating the at least one user-supplied risk parameter on a user system; receiving at least one user-supplied risk parameter associated with the counterparty; receiving a first instruction authorizing payment from the account holder to the counterparty; storing the first instruction in a payment queue; during processing of a foreign exchange payment-based transaction, performing a risk filter routine that determines whether to selectively reject payment authorized by the first instruction based upon the at least one user-supplied risk parameter associated with the counterparty; wherein said risk filter routine automatically generates an available balance for the counterparty based upon the at least one user-supplied risk parameter, payments made by the account holder, and payments received by the account holder; automatically accesses said first instruction stored in the payment queue; and automatically determines whether to selectively reject payment authorized by the first instruction based upon the available balance; wherein said risk filter routine automatically rejects payment authorized by the first instruction in the event that the amount of payment authorized by the first instruction exceeds the available balance; and wherein the risk filter routine automatically returns the first instruction to the payment queue for later re-evaluation.