Companies that sell products and goods will have inventory and cost of goods sold accounts. The basic cost of goods sold equation is: Beginning Inventory + Purchases - Ending Inventory = Cost of Goods Sold Ending inventory of one period is the beginning inventory of the next period. Businesses that offer services do not normally sell products as their primary business activity but may sell them to supplement their services. What additional accounts would you expect to find in a manufacturing firm and how do they relate to cost of goods sold?