Periodic Inventory System


The periodic inventory system, as the name suggests records inventory balance on hand periodically, specifically, at the beginning and end of a set accounting period.

Under the periodic inventory, all purchases made between inventory counts are placed under the purchases account. When the next physical inventory is done, the balance of the purchases account is shifted to the inventory account to match the cost of ending inventory.

Calculation of Periodic Inventory System

The cost of goods sold under the periodic inventory system is calculated thus-

Beginning inventory + Purchases = Cost of goods available for sale

Cost of goods available for sale – Ending inventory = Cost of goods sold

Let’s understand this with an example.

A company ABC has a beginning inventory of $100,000, has paid $150,000 for purchases, and its physical inventory count reveals an ending inventory cost of $90,000. The calculation of the cost of goods sold is:

$100,000 Beginning inventory + $150,000 Purchases – $90,000 Ending inventory

= $160,000 Cost of goods sold

Difference between Periodic inventory system and Perpetual Inventory System

Considering periodic inventory system vs perpetual inventory system in that, the former is based on physical counting of inventory at the beginning and end of an accounting period, while the latter uses software like an inventory management software to update inventory in real-time.

In the perpetual inventory system, the stock count is updated continuously, meaning with every piece of inventory that arrives or is sold. In contrast, inventory is updated at periodic intervals.

The periodic inventory system provides information about the inventory and cost of goods sold whereas the perpetual inventory system gives information about inventory and sales.

In the perpetual inventory system, any loss of goods is included in the closing inventory. On the other hand, in the periodic inventory system, the same is recorded in cost of goods sold.

In the periodic inventory system, since no software is used, it becomes affordable for smaller businesses who may not be able to invest in sophisticated software, unlike those using a perpetual inventory system.

In the perpetual inventory system, physical counting does not interfere with daily business operations, meaning businesses do not have to shut down to take a stock count in the warehouse.


The periodic inventory system is less expensive when compared with the perpetual inventory system. However, it cannot beat the accuracy of the perpetual inventory system, where inventory is maintained continuously with every purchase and sale. The periodic inventory system is more suitable for small businesses who do not require dedicated software for inventory management due to low sales volume or because they cannot afford it. Yet some companies prefer the periodic inventory system since it is less demanding as warehouse managers do not have to constantly update inventory on the system.