In a process costing system, when manufacturing overhead costs are applied to the cost of production, they are debited to:

The Work in Process Inventory account.

Explanation:

Process costing can be defined as a cost accounting method used for assigning manufacturing or production costs to the units of goods produced by a business firm over a specific period of time. It is mostly used by firms that produce a large quantity of homogeneous or similar products on a continuous basis. Process costing typically uses more than one Work in Process Inventory account because costing at each stage of production or manufacturing process.

In a process costing system, when manufacturing overhead costs are applied to the cost of production, they are debited to the Work in Process Inventory account.

In the manufacturing process, partially or partly completed goods that are still in the process of being converted into a finish product are defined as work-in-process inventories.

Generally, the work-in-process inventories include the following raw materials cost, direct labor cost and factory overhead cost.

These category of products are only partially completed and as such are waiting for further processing, still undergoing fabrication or kept in a buffer storage.

In conclusion, Process costing typically uses a separate Work in Process Inventory account for each department while job order costing typically uses only one Work in Process Inventory account for each product.