The regulatory mechanism of the SBUS resided in its fiscal duties as depository for the US Department of the Treasury. As such, the bank accepted circulating state bank paper money from individuals, businesses and importers when they paid taxes or custom duty fees. The central bank immediately credited these payments to the US Treasury with its own metallic reserves. The SBUS, in turn, anticipated that the state banks which had issued the paper money would, upon demand, redeem their currency with gold and silver—"convertibility"—reimbursing the government bank.