Perpetual vs Periodic Inventory: Journal Entries Compared
Perpetual vs periodic inventory comes down to when cost of goods sold (COGS) is recorded. A perpetual system updates Inventory with every purchase and records COGS at every sale. A periodic system records purchases in temporary accounts such as Purchases and calculates COGS only at period-end, using a physical count of ending inventory.
The distinction matters whenever a question asks for a journal entry on a specific date. Both businesses can report the same sales, ending inventory, and gross profit for a period. Their entries on the day a customer buys an item can look quite different.
Video: compare journal entries under both inventory systems
In this lecture segment (6:12 to 13:40), you’ll see the same purchase, return, and sale recorded side by side under each system. Watch this segment on YouTube.
Perpetual vs periodic inventory: what is the difference?
Imagine a customer buying a $50 item that cost the store $30. The cash register captures the $50 selling price. A perpetual system also looks up the cost attached to that item and removes $30 from Inventory. A periodic system waits until the period closes to determine how much of the available cost has left inventory.
| Transaction or record | Perpetual system | Periodic system |
|---|---|---|
| Buy goods on credit | Debit Inventory. Credit Accounts Payable. | Debit Purchases. Credit Accounts Payable. |
| Pay inbound freight on the goods | Debit Inventory. Credit Cash. | Debit Freight-In. Credit Cash. |
| Return goods to supplier for credit | Debit Accounts Payable. Credit Inventory. | Debit Accounts Payable. Credit Purchase Returns and Allowances. |
| Take a purchase discount under the gross method | Credit Inventory for the discount. | Credit Purchase Discounts for the discount. |
| Sell merchandise | Record revenue and the cost of the units sold. | Record revenue. Calculate COGS at period-end. |
| Use a physical count | Compare counted quantities with item records, investigate differences, and record any confirmed shortage by crediting Inventory. | Use counted quantities and unit costs to determine ending inventory. |
Purchases is a temporary account used to gather merchandise costs. It is closed at period-end. Inventory is an asset account, and its ending balance carries into the next period. A perpetual system commonly maintains a subsidiary ledger with quantities and costs by item. (New to subsidiary ledgers? See special journals and subsidiary ledgers explained.) The total of those detailed records should agree with the inventory control account.
Worked example: record a purchase, a return, and a sale
Suppose Beacon Desk Supply begins April with 20 lamps costing $18 each. It buys 50 more at $18 on account, returns five of those lamps to the supplier for credit, and sells 40 lamps on account for $31 each. A count at month-end finds 25 lamps. Assume there are no other transactions, freight charges, discounts, or losses.
| April transaction | Perpetual entry | Periodic entry |
|---|---|---|
| Purchase 50 × $18 | Debit Inventory $900. Credit Accounts Payable $900. | Debit Purchases $900. Credit Accounts Payable $900. |
| Return 5 × $18 | Debit Accounts Payable $90. Credit Inventory $90. | Debit Accounts Payable $90. Credit Purchase Returns and Allowances $90. |
| Record sales revenue, 40 × $31 | Debit Accounts Receivable $1,240. Credit Sales Revenue $1,240. | Debit Accounts Receivable $1,240. Credit Sales Revenue $1,240. |
| Record the cost of 40 lamps | Debit COGS $720. Credit Inventory $720. | No cost entry on the sale date. |
Before the count, the perpetual Inventory balance is $360 + $900 − $90 − $720 = $450. The physical count confirms 25 lamps at $18, also $450. Under periodic accounting, the Inventory account still shows the $360 beginning balance until the closing entry is posted. That balance can’t tell you how many lamps are on the shelf at any point during April, so the business relies on the count.
How does the periodic closing entry work?
Start with $360 of beginning inventory and add purchases of $900 less the $90 supplier return. The $1,170 total is the cost of goods available for sale. Subtract counted ending inventory of $450 to obtain $720 of COGS. The following compound entry is one way to clear the temporary accounts and replace the opening inventory balance with the counted balance.
| Account | Debit | Credit |
|---|---|---|
| Inventory (ending) | $450 | — |
| Cost of Goods Sold | $720 | — |
| Purchase Returns and Allowances | $90 | — |
| Purchases | — | $900 |
| Inventory (beginning) | — | $360 |
| Totals | $1,260 | $1,260 |
The two Inventory lines refer to the same ledger account. Crediting $360 removes its opening balance. Debiting $450 establishes the closing balance. The resulting gross profit is $1,240 of revenue less $720 of COGS, or $520 under either system in this example. To see how the remaining temporary accounts, such as sales discounts and sales returns, are closed, follow the closing entries for a merchandising company.
Which inventory system should a business use?
A perpetual system makes sense when a business needs up-to-date quantities and costs, for example to reorder stock, spot theft, or prepare monthly statements without a full count. Barcode scanners and point-of-sale software do most of the record keeping, so it’s common in businesses that scan items at checkout.
A periodic system is simpler and cheaper to run. It can suit a small business with a few low-cost items, where tracking the cost of every single sale would cost more than it’s worth. The tradeoff is that the business doesn’t know its COGS or gross profit until it counts inventory, and it can’t easily separate losses from sales.
| Feature | Perpetual system | Periodic system |
|---|---|---|
| Inventory balance during the period | Current after every transaction | Shows the beginning balance until the period-end entry |
| Cost of goods sold | Recorded at each sale | Calculated at period-end |
| Spotting shortages | A count compared with the records reveals them | Losses are mixed into COGS |
| Record-keeping cost | Higher, usually needs software | Lower |
| Physical count | Still needed to verify the records | Required to calculate COGS |
Neither U.S. GAAP nor IFRS requires a particular record-keeping system. The rules for measuring inventory come from FASB ASC 330, Inventory, and IAS 2, Inventories. FASB is the Financial Accounting Standards Board, which sets U.S. accounting standards.
Do both systems give the same COGS under FIFO, LIFO, and average cost?
In the lamp example, every unit cost $18, so both systems produced $720 of COGS. When unit costs change during the period, the answer depends on the cost flow assumption, which is the rule for deciding which costs leave inventory first.
First-in, first-out (FIFO) gives the same COGS under both systems, as long as there is no shrinkage. Last-in, first-out (LIFO) and average cost can give different results, because a perpetual system assigns costs on each sale date using only the units on hand at that moment. Under the average method, the perpetual version is called moving average and the periodic version is called weighted average. LIFO is permitted under U.S. GAAP and prohibited under IFRS.
For a full worked comparison with numbers, see periodic vs perpetual inventory costing with FIFO, LIFO, and average cost.
How to avoid the common journal-entry errors
Read the verb in the question. “Purchased” calls for an acquisition entry. “Sold” calls for sales revenue, and under perpetual accounting also triggers a cost entry. “Counted” calls for a check against the books or a period-end calculation, depending on the system.
Keep supplier returns separate from customer returns. Beacon returned five lamps to the supplier, so its payable fell. Customer returns use different entries, covered in sales returns and allowances journal entries. Also mark the two prices on your scratch paper: $31 is revenue per lamp and $18 is the cost to remove per lamp. Multiplying 40 by the selling price in both entries would eliminate the reported gross profit.
For the reporting categories behind Inventory, review the types of inventory and their cost flow. When book quantities and a reliable count disagree, use the inventory shrinkage reconciliation. For another accounting reference, see OpenStax’s comparison of the two systems.
Key takeaways
- A perpetual system debits Inventory for purchases and records COGS at every sale.
- A periodic system debits Purchases and calculates COGS at period-end: beginning inventory plus net purchases, minus counted ending inventory.
- Net purchases means purchases plus freight-in, minus purchase returns, allowances, and discounts.
- Both systems record sales revenue the same way on the sale date.
- Both systems still need a physical count. Perpetual uses it to check the records, and periodic uses it to calculate COGS.
- When unit costs are the same, both systems report the same results. In the Beacon Desk Supply example, both show $720 of COGS and $520 of gross profit.
Interactive practice on perpetual and periodic inventory
Work through five questions on purchase entries, freight-in, supplier returns and discounts, the inventory subsidiary ledger, and when to record cost of goods sold. For periodic inventory, calculate cost of goods sold by subtracting counted ending inventory from the cost of goods available for sale.
Practice questions and answers
A retailer using periodic inventory buys $640 of merchandise on credit. Which account does it debit?
Debit Purchases $640 and credit Accounts Payable $640. The Inventory account is updated during the closing process.
A perpetual-system retailer sells three items for $70 each. Each cost $42. What are the two amounts recorded?
Record revenue of $210 and separately debit COGS and credit Inventory for $126. The $84 difference is gross profit.
Beginning inventory is $1,500, net cost of purchases is $4,700, and counted ending inventory is $1,850. What is periodic COGS?
Goods available cost $6,200. Subtract ending inventory of $1,850 to obtain COGS of $4,350.
Frequently asked questions
Do both systems record a credit sale on the sale date?
Yes. Both debit Accounts Receivable and credit Sales Revenue for the selling price. The timing difference concerns the inventory cost.
Does a perpetual system eliminate physical counts?
No. A running balance shows what the records say should exist. A count can reveal damage, missing units, or posting errors.
Can a periodic system tell how much of COGS represents lost merchandise?
The basic calculation cannot separate loss from sales. Both reduce counted inventory, so the residual COGS may include both.
Is Purchases an asset account?
No. Purchases is a temporary account with a normal debit balance. It collects the cost of merchandise bought during the period, feeds into the cost of goods sold calculation, and is closed to zero at period-end. Inventory is the asset account.
Which inventory system is more accurate?
A perpetual system provides more timely inventory and COGS information, and comparing its records with a physical count helps identify shortages. Both systems can produce the same period-end totals when their costing assumptions and inventory adjustments lead to the same assigned costs. When unit costs change, perpetual and periodic LIFO or average cost can produce different results. The periodic Inventory account does not provide an updated inventory cost balance during the period.
How do you calculate cost of goods sold under a periodic system?
Add beginning inventory and net purchases to get the cost of goods available for sale, then subtract counted ending inventory. Net purchases are purchases plus freight-in, minus purchase returns, allowances, and discounts. In the lamp example, $360 + $810 − $450 = $720.
About the author: Mansour Farhat, CPA, CIA, DBA, creates the accounting and exam-prep lessons on Farhat Lectures and its YouTube channel, where he teaches students and CPA, CMA, and EA candidates.
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