10.2 The Perpetual Inventory Method & Transaction Entries
Key Takeaways
- A perpetual merchandiser updates Inventory after every purchase, return, discount, sale, sales return, and shrinkage entry, so the Inventory account is a running balance.
- Every credit sale needs two entries: debit Accounts Receivable and credit Sales for the selling price, and debit Cost of Goods Sold and credit Inventory for the cost of the units that left.
- Purchases debit Inventory (not Purchases). Freight-in the buyer pays is also debited to Inventory. Purchase returns and cash discounts taken credit Inventory so remaining units carry net cost.
- Redbridge Hardware’s 80 tarps cost $2,080 after $80 freight-in, or $26 each; selling 30 tarps records Sales of $1,350 and Cost of Goods Sold of $780.
- A physical count still matters under perpetual records: units missing versus the book quantity are inventory shrinkage, credited out of Inventory at the carrying cost of the missing units.
What “perpetual” actually updates
Under the perpetual inventory method, the Inventory account is a running total. Each purchase, purchase return, purchase allowance, cash discount taken, sale, sales return, and shrinkage adjustment posts to Inventory when the event happens. Cost of Goods Sold is recorded at each sale, not only at year-end. Barcode systems and inventory modules make this the default in modern software, but the CB inventory workbook still expects you to write the manual journal entries as if you were posting a stock card.
Periodic books (section 10.3) use a Purchases temporary account and wait until the physical count to compute COGS. Do not mix the account names. If the problem says perpetual, there is no Purchases account in the journal.
AIPB’s Mastering Inventory perpetual section walks purchases at gross or net, sales, discounts, returns and allowances, customer sales returns, and shrinkage. This independent OpenExamPrep section teaches those same event types with original Redbridge Hardware numbers. It is not an AIPB workbook reprint.
Purchases and freight-in debit Inventory
Redbridge Hardware buys 80 canvas tarps on June 3 at $25 each, invoice $2,000, terms 2/10, n/30, FOB shipping point. Redbridge pays Yellow Line Freight $80 cash the same day.
Dr Inventory 2,000
Cr Accounts Payable 2,000
Dr Inventory 80
Cr Cash 80
Inventory now holds $2,080. Unit cost is $2,080 ÷ 80 = $26. Combining the two debits into one Inventory line of $2,080 is acceptable if the problem gives a single composite cost. Splitting them shows that the vendor payable is $2,000 and the carrier was paid separately.
If the terms had been FOB destination and the seller paid the carrier, Redbridge would not debit Inventory for freight. The seller would debit Freight-out (or Delivery Expense). Redbridge’s Inventory would be $2,000, or $25 per tarp.
Purchase returns and allowances
Keep the 80-tarp lot intact for the sale example below. Returns are easier to journal on a different SKU. On June 5 Redbridge returns 8 garden hoses that arrived cracked. Those hoses had been recorded at $25 each, so the vendor issues a $200 credit memorandum. Freight on that hose shipment is not refunded.
Dr Accounts Payable 200
Cr Inventory 200
The hose lot’s remaining units keep any unreimbursed freight, so their unit cost ticks up if you recompute. Many exam items avoid that fraction by putting the return before freight is recorded, or by having the seller also credit freight. When the problem is silent, return the units at the invoice unit price that was recorded, and leave freight with the remaining lot unless told to reallocate.
A purchase allowance keeps the goods. The vendor reduces the price, for example $60 for scuffed grommets on a separate hardware invoice. The entry is the same shape — debit Accounts Payable, credit Inventory — without a quantity change. Remaining units simply carry less cost.
Cash discounts under perpetual records
Use a clean second invoice so the discount math stays in whole dollars. On June 10 Redbridge buys $4,000 of rope on account, terms 2/10, n/30, and records gross:
Dr Inventory 4,000
Cr Accounts Payable 4,000
Redbridge pays on June 18, day 8:
Dr Accounts Payable 4,000
Cr Inventory 80
Cr Cash 3,920
The $80 credit to Inventory (2% × $4,000) is the perpetual-gross way to take a cash discount. Remaining rope now carries $3,920. There is no Purchase Discounts contra account on perpetual books in the usual exam presentation; the cost reduction goes straight to Inventory.
Net method on the same invoice records $3,920 from the start:
Dr Inventory 3,920
Cr Accounts Payable 3,920
Pay on time: debit Accounts Payable $3,920, credit Cash $3,920. Miss the window:
Dr Accounts Payable 3,920
Dr Purchase Discounts Lost 80
Cr Cash 4,000
Purchase Discounts Lost is not added to Inventory. The merchandise already sits at the intended net cost; the extra $80 is the cost of paying late.
If Redbridge returns part of a gross-method purchase before paying, compute the 2% on the remaining payable, not on the original invoice. A $4,000 purchase with a $500 return leaves $3,500 subject to 2% ($70), not $80.
Two entries on every sale
The 80-tarp lot is still $2,080, or $26 each (the hose return did not touch these units). On June 20 Redbridge sells 30 tarps on account at $45 each = $1,350.
Revenue entry:
Dr Accounts Receivable 1,350
Cr Sales 1,350
Cost entry:
Dr Cost of Goods Sold 780
Cr Inventory 780
$780 is 30 × $26. After the sale, 50 tarps remain at $26 = $1,300. Gross profit on the invoice is $1,350 − $780 = $570.
The exam trap is recording only the revenue line. Perpetual books that skip the COGS entry overstate Inventory and understate COGS until someone notices the stock card. Cash sales replace Accounts Receivable with Cash; the COGS entry does not change.
Customer sales returns
On June 22 a contractor returns 4 tarps that were the wrong size. They can go back on the shelf. Selling price $45 × 4 = $180. Cost $26 × 4 = $104.
Dr Sales Returns and Allowances 180
Cr Accounts Receivable 180
Dr Inventory 104
Cr Cost of Goods Sold 104
Both halves reverse. Restoring only the revenue side leaves Inventory too low and COGS too high. Restoring Inventory at current replacement cost instead of the $26 carrying amount that left on June 20 would smuggle a gain or loss into the return. Put the units back at the cost that was stripped out, which under FIFO (section 10.4) means the layer costs that were assigned to that sale.
If the returned tarps are unsaleable, do not debit Inventory. Debit an inventory write-down, supplies (if salvaged for shop use), or loss, and still reverse the $180 of revenue. Damaged returns are not merchandise available for sale.
Shrinkage is the reason you still count
After the June 20 sale and the June 22 customer return, perpetual records show 54 tarps (80 − 30 + 4) at $26 = $1,404. On June 30 the warehouse counts 51 tarps. 3 units are missing. Shrinkage = 3 × $26 = $78.
Dr Inventory Shrinkage Expense 78
Cr Inventory 78
Some firms debit Cost of Goods Sold instead of a separate shrinkage account. Either way, Inventory must fall to the count. The physical count under perpetual is not how you first compute COGS. COGS was already recorded on June 20 (and reversed in part on June 22). The count catches theft, breakage, and bookkeeping quantity errors.
If the count is higher than the books, do not silently debit Inventory and credit COGS without investigating. Overages can mean unrecorded purchases, sales recorded twice, or units counted that are consigned-in. Fix the underlying error; do not invent income.
Perpetual document flow versus periodic
| Event | Perpetual accounts | Periodic accounts (preview) |
|---|---|---|
| Purchase of merchandise | Dr Inventory, Cr AP | Dr Purchases, Cr AP |
| Freight-in (buyer) | Dr Inventory, Cr Cash/AP | Dr Freight-in, Cr Cash/AP |
| Purchase return / allowance | Dr AP, Cr Inventory | Dr AP, Cr Purchase Returns and Allowances |
| Cash discount taken (gross) | Dr AP, Cr Inventory, Cr Cash | Dr AP, Cr Purchase Discounts, Cr Cash |
| Sale | Dr AR, Cr Sales and Dr COGS, Cr Inventory | Dr AR, Cr Sales only |
| Sales return of good units | Reverse both the revenue and the COGS/Inventory entries | Reverse revenue only; the count will pick up the units |
| Period-end count | Adjust shrinkage | Compute COGS from the inventory equation |
The running Inventory balance is why perpetual FIFO (section 10.4) can cost each sale from the layers on the stock card that day. Periodic FIFO waits until you know how many units are left, then peels the oldest costs from the whole period’s purchases.
Exam traps for section 10.2
- Debiting Purchases on a perpetual problem.
- Recording the sale without the COGS / Inventory pair.
- Crediting Purchase Discounts under perpetual-gross instead of crediting Inventory.
- Putting buyer freight-in in Freight-out or Delivery Expense.
- Restoring a sales return at retail price inside Inventory.
- Skipping the shrinkage entry because “perpetual already has the right inventory.” The books have a running total; the warehouse has the truth about missing units.
Redbridge Hardware uses a perpetual system. It sells 30 tarps on account for $1,350. The tarps carry $780 of inventory cost. Which pair of entries is required on the sale date?
Under the perpetual method, Redbridge buys 80 tarps for $2,000 FOB shipping point and pays $80 freight to the carrier. How is the purchase recorded?
Redbridge records purchases at gross. It bought merchandise for $4,000, terms 2/10, n/30, and pays on day 8. What happens to Inventory when the cash discount is taken?