The accounting for inventory involves determining the correct unit counts comprising ending inventory, and then assigning a value to those units. The resulting costs are then used to record an ending inventory value, as well as to calculate the cost of goods sold for the reporting period. These basic inventory accounting activities are expanded upon in the following bullet points:
- Determine ending unit counts. A company may use either a periodic or perpetual inventory system to maintain its inventory records. A periodic system relies upon a physical count to determine the ending inventory balance, while a perpetual system uses constant updates of the inventory records to arrive at the same goal.
- Improve record accuracy. If a company uses the perpetual inventory system to arrive at ending inventory balances, the accuracy of the transactions is paramount.
- Conduct physical counts. If a company uses the periodic inventory system to create ending inventory balances, the physical count must be conducted correctly. This involves the completion of a specific series of activities to improve the odds of counting all inventory items.
- Estimate ending inventory. There may be situations where it is not possible to conduct a physical count to arrive at the ending inventory balance. If so, the gross profit method or the retail inventory method can be used to derive an approximate ending balance.
- Assign costs to inventory. The main role of the accountant on a monthly basis is assigning costs to ending inventory unit counts. The basic concept of cost layering, which involves tracking tranches of inventory costs, involves the first in, first out (FIFO) layering system and the last in, first out (LIFO) system. A different approach is the assignment of a standard cost to each inventory item, rather than a historical cost.
- Allocate inventory to overhead. The typical production facility has a large amount of overhead costs, which must be allocated to the units produced in a reporting period.
The preceding bullet points cover the essential accounting for the valuation of inventory. In addition, it may be necessary to write down the inventory values for obsolete inventory, or for spoilage or scrap, or because the market value of some goods have declined below their cost. There may also be issues with assigning costs to joint and by-product inventory items. We expand upon these additional accounting activities in the following bullet points:
- Write down obsolete inventory. There must be a system in place for identifying obsolete inventory and writing down its associated cost.
- Review lower of cost or market. The accounting standards mandate that the carrying amount of inventory items be written down to their market values (subject to various limitations) if those market values decline below cost.
- Account for spoilage, rework, and scrap. In any manufacturing operation, there will inevitably be certain amounts of inventory spoilage, as well as items that must be scrapped or reworked. There is different accounting for normal and abnormal spoilage, the sale of spoiled goods, rework, scrap, and related topics.
- Account for joint products and by-products. Some production processes have split-off points at which multiple products are created. The accountant must decide upon a standard method for assigning product costs in these situations.
- Disclosures. There are a small number of disclosures about inventory that the accountant must include in the financial statements.