Periodic Inventory System: Definition, Advantages & Examples

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  • 0:01 Periodic Inventory System
  • 1:10 Inventory Management…
  • 3:06 Example
  • 4:54 Advantages & Disadvantages
  • 6:12 Lesson Summary
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Lesson Transcript
Instructor: Kimberly Winston

Kimberly has a MBA in Logistics & Supply Chain Management

Business owners use inventory systems to track and update inventory. This lesson defines the periodic inventory system, outlines its advantages and disadvantages, and demonstrates its use with an example.

Periodic Inventory System

For any business that carries inventory, or products stored for future sale, it is necessary to keep track of what is currently on hand. Some businesses keep track of inventory using a periodic inventory system. A periodic inventory system is an inventory system that updates inventory at the end of a specified period of time. This may mean that they update their inventory records at the end of each month, quarter, or year. Whenever the period ends, it generally coincides with the end of a reporting period, or a timeframe for which a report is drawn on all financial activities that occurred during that time. Common reporting periods conclude on a quarterly or annual basis.

Since a periodic inventory system only keeps track of inventory periodically throughout the year and not as inventory is purchased or sold, a physical count of the inventory must be conducted. A physical count is a complete and exact count of each item in the inventory done by hand. Some businesses carry hundreds or thousands of products, so physical counts can be extremely time-consuming. Even for businesses that carry few products, physical counts can be tedious and may take a lot of time to complete if problems, such as missing parts or wrong counts, arise.

Inventory Management Between Counts

Inventory purchases made between physical counts are recorded in a purchases account, a ledger used to record all inventory purchases and their cost. We'll try to break it down as simply as possible.

The purchases account begins with the beginning balance of inventory, a complete and thorough record of the cost of all of the items the company has acquired that will be resold. Throughout the recording period, additional inventory purchases are logged into the same ledger. These entries track only inventory goods, items that will be resold. Entries include the number of each item purchased, how much these items cost, and other pertinent information, such as from which vendor and the date.

At the end of the recording period, the purchases account will be balanced and the numbers it generates will be compared to the physical count. Adding the inventory's beginning balance, the amount of money spent on inventory items at the start of the recording period, to the total amount of money spent on additional inventory shipments throughout the same recording period will result in the cost of goods for sale.

At this point, the physical count will be conducted. This physical count will tell how much inventory is in stock. Based on records, businesses can then calculate how much the inventory is worth, or the ending balance. By subtracting the ending balance, the worth of the inventory on hand at the end of a reporting period, from the cost of goods for sale, the company can determine how much inventory was sold during the period and for how much money. This final number is called the cost of goods sold, or COGS.

The formula for this process is Beginning Balance of Inventory + Cost of Inventory Purchases = Cost of Goods for Sale
Cost of Goods for Sale - Cost of Ending Inventory = Cost of Goods Sold (COGS).


Let's take a look at an example to help clear this up. Just to keep it simple, we'll stick with a retail store that sells exactly one thing - envelopes.

The Envelope Store uses the periodic inventory system. Its reporting periods are quarterly, running January through March, April through June, July through September, and October through December. On January 1, the store records in the purchases account the beginning balance of inventory as $15,520. From January 1 through March 31, the store orders three shipments of additional envelopes, each at a cost of $2,250.

At the end of the quarter, the Envelope Store conducts a physical count of all the inventory on hand. They find after counting the envelopes and totaling their cost that the ending inventory for the quarter is $8,450 worth of envelopes. The question is how much was the Envelope Store's COGS for the first quarter of the year?

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