A billing system includes an operation unit, a determination unit, an extraction unit, a first calculator, and a second calculator. The operation unit receives an operation for executing a function provided by one device of a plurality of devices. The determination unit determines whether the one device is available for the function associated with the operation received by the operation unit. The extraction unit extracts another device that is available for the function as a substitute for the one device when the determination unit determines that the one device is not available for the function. The first calculator calculates a fee for the function to be executed by the other device. The second calculator calculates a total billed amount based on the fee calculated by the first calculator and content executed by the other device when the function is executed by the other device.