The Imprest system is a form of financial accounting system. The most common imprest system is the petty cash system. The base characteristic of an imprest system is that a fixed amount is reserved, which will be replenished at the end of a period or when the circumstances request it. This replenishment is not credited on the imprest account, but from another source. When a sufficient amount is used, the imprest account will never be credited again. As such, it can be seen as a permanent debt.