What Is the Periodic Inventory System?

What Is the Periodic Inventory System?

The periodic inventory system is a method where a company updates its inventory records only at the end of an accounting period, rather than after every transaction. It relies on a physical count to determine ending inventory and cost of goods sold, making it simpler for businesses with high volume or low-value items.

How the Periodic System Works

Under this approach, purchases are recorded in a temporary "Purchases" account, not in the inventory ledger. When a sale occurs, the cost of goods sold is not updated immediately. Instead, at period-end, the company performs a physical count, calculates the cost of ending inventory, and subtracts it from the goods available for sale to derive cost of goods sold. The formula is: Beginning Inventory + Purchases − Ending Inventory = Cost of Goods Sold.

Key Components

• Purchases Account: Aggregates all inventory acquisitions during the period.
• Physical Count: A manual tally of stock on hand at period-end.
• Gross Profit Method: An estimation technique used when a full count is impractical.

Periodic vs. Perpetual Inventory Systems

A perpetual system updates inventory continuously after each sale and purchase, providing real-time data. The periodic system defers updates until the close of the period, trading timeliness for simplicity and lower record-keeping costs.

Comparison Table

Advantages and Limitations

The periodic system reduces administrative overhead and is well-suited for small businesses or those selling low-cost, high-volume goods. Its main limitation is the lack of up-to-date inventory visibility, which can obscure stockouts or shrinkage during the period and make timely decision-making difficult.