The fixed costs of a manufacturing facility include lease or mortgage payments, salaries for permanent employees, benefits and insurance. Direct costs include only the labor and materials As the name suggests, non-manufacturing overheads are the costs that are not incurred in the manufacturing process of the product hence these costs are not attributable to this process. These costs are the expenses occurred in the other apart from the manufacturing are usually classified under the head of Selling, Admin and General Expenses. The interest expense also falls in the same category and since these are non-manufacturing overheads, they are simply reported under the expenses while preparing the income statement of the company.