# Perpetual Inventory Methods and Formulas

The Inventory balance is \$352.50 (4 books with an average cost of \$88.125 each). The company has made the following purchases and sales during the month of January 2016. The use of FIFO method is very common to compute cost of goods sold and the ending balance of inventory under both perpetual and periodic inventory systems. The example given below explains the use of FIFO method in a perpetual inventory system.

Perpetual FIFO is a cost flow tracking system under which the first unit of inventory acquired is presumed to be the first unit consumed or sold. There is no difference between the resulting charge to the cost of goods sold if a perpetual inventory system or a periodic inventory system is used. After Corner Bookstore makes its third purchase of the year 2022, the average cost per unit will change to \$88.125 ([\$262.50 + \$90] ÷ 4). As you can see, the average cost moved from \$87.50 to \$88.125—this is why the perpetual average method is sometimes referred to as the moving average method.

## Perpetual FIFO

If you want to understand its use in a periodic inventory system, read “first-in, first-out (FIFO) method in periodic inventory system” article. Each sale of inventory requires two entries to be made in the journal. The first should record the sale value by debiting the accounts receivable account and crediting the sales account. The second should record the cost of goods sold by debiting the cost of goods sold account and crediting the inventories account. If the perpetual inventory system is used, the inventory account and the cost of goods sold account are updated each time when a purchase or a sale is made.

• The first should record the sale value by debiting the accounts receivable account and crediting the sales account.
• In turn, each purchase of inventory is recorded by debiting the purchases account and crediting the accounts payable account.
• In other words, the ending inventory was counted and costs were assigned only at the end of the period.
• After Corner Bookstore makes its third purchase of the year 2022, the average cost per unit will change to \$88.125 ([\$262.50 + \$90] ÷ 4).
• Under first-in, first-out method, the ending balance of inventory represents the most recent costs incurred to purchase merchandise or materials.

Under that system, the ending inventory is calculated as the sum of the beginning inventory and total purchases during the relevant period less units sold. With perpetual LIFO, the last costs available at the time of the sale are the first to be removed from the Inventory account and debited to the Cost of Goods Sold account. Since this is the perpetual system we cannot wait until the end of the year to determine the last cost (as is done with periodic LIFO). An entry is needed at the time of the sale in order to reduce the balance in the Inventory account and to increase the balance in the Cost of Goods Sold account. The preceding illustrations were based on the periodic inventory system. In other words, the ending inventory was counted and costs were assigned only at the end of the period.

## What is Perpetual FIFO?

With the help of the above inventory card, we can easily compute the cost of goods sold and ending inventory. Under first-in, first-out method, the ending balance of inventory represents the most recent costs incurred to purchase merchandise or materials. Perpetual FIFO is one of the most common cost flow tracking systems in use today, because it accurately reflects the actual flow of goods through a business. Let’s calculate the inventory balance on 31st of March and cost of goods sold (COGS) using the FIFO inventory method. Let’s assume that a company has bought 55 units to replenish stock (Figure 3).

• The idea behind this method is that inventories bought first should be sold first.
• Each sale of inventory requires two entries to be made in the journal.
• The Inventory balance is \$352.50 (4 books with an average cost of \$88.125 each).
• When using the perpetual system, the Inventory account is constantly (or perpetually) changing.

In turn, the balance of the inventory account amounts to the cost of 30 units of Batch 2, the cost of Batch 3, and the cost of Batch 4. The following table, ledgers, and financial statements reveal the application of perpetual LIFO. Note that the results usually differ from the periodic LIFO approach.

## Gross Profit Method

The first-in, first-out or FIFO inventory method is used to compute the cost of goods sold (COGS) and the inventory account balance at the end of the relevant period. The idea behind this method is that inventories bought first should be sold first. In other words, inventories have to be assigned to cost of goods sold in the order they entered the stock. The average method can be applied on a perpetual basis, earning it the name moving average.

The ending inventory of 43,000 units is fully represented by the purchase made on 4th of March, so the ending balance of the inventory account is \$7,310,000. If the bookstore sells the textbook for \$110, its gross profit under perpetual LIFO will be \$21 (\$110 – \$89). Note that this \$21 is different than the gross profit of \$20 under periodic LIFO. As with the periodic system, observe that the perpetual system also produced the lowest gross profit via LIFO, the highest with FIFO, and the moving-average fell in between. When using the perpetual system, the Inventory account is constantly (or perpetually) changing.

The journal entries are not repeated here but would be the same as with FIFO; only the amounts would change. In other words, the costs to acquire merchandise or materials are charged against revenues in the order in which they are incurred. Each purchase of inventory is recorded by debiting the inventory account and crediting the accounts payable account.

## The Definitive Guide to Perpetual Inventory

With a perpetual system, a running count of goods on hand is maintained at all times. Modern information systems facilitate detailed perpetual cost tracking for those goods. When using the perpetual inventory system, the Inventory account is constantly (or perpetually) changing. Thus, the cost of goods sold totals \$37,765,000, and the ending inventory account balance is \$7,310,000. The cost of Batch 1 and the cost of 30 units of Batch 2 should be assigned to the cost of goods sold.

## What Is a Perpetual Inventory System?

The beginning inventory of 195 units is composed of 4 batches shown in the order they arrived (Batch 1 is the oldest one). When we sell identical goods, we can choose from several inventory costing methods when calculating Cost of Goods Sold and Ending Inventory. Harold Averkamp (CPA, MBA) has worked as a university accounting instructor, accountant, and consultant for more than 25 years. Thus, the cost of goods sold in the first quarter amounts to \$37,765,000.