Under absorption costing, fixed manufacturing overhead costs are included in product costs, along with direct materials, direct labor, and variable manufacturing overhead. If some of the units are not sold by the end of the period, then they are carried into the next period as inventory. The fixed manufacturing overhead cost attached to the units in ending inventory follows the units into the next period. When the units are finally sold, the fixed manufacturing overhead cost that has been carried over with the units is included as part of that period’s cost of goods sold.