Maintenance involves those activities and costs incurred to preserve the operational status of an asset until the end of its expected useful life. These activities involve counteracting the ongoing wear and tear imposed on an asset. Maintenance costs are charged to expense as incurred. If an expenditure improves an asset or extends its useful life, the cost is instead added to the cost of the asset and charged to expense over a longer period of time, in the form of depreciation.

Examples of maintenance are the costs incurred to replace air filters in a machine, the labor required to replace a broken part in a vehicle, and the labor required to apply a fresh coat of paint to a building.