Two product costing methods commonly used in manufacturing companies are absorption costing and variable costing. Absorption costing is used for determining product costs and cost of goods sold for external financial reporting in many countries. It treats both variable and fixed manufacturing costs as product costs. This is in contrast to variable costing, under which only variable manufacturing costs are treated as product costs. Fixed manufacturing overhead is treated as a period cost and is charged off in its entirety against revenue in the period in which they occurred.