Dictionary / Perpetual Inventory
What does Perpetual Inventory mean in accounting?
Quick definition
Inventory & costingA book inventory kept in continuous agreement with stock on hand by means of a detailed record that may also serve as a subsidiary ledger where dollar amounts as well as physical quantities are maintained. This term guides how bookkeepers record, classify, and explain related transactions in routine financial reporting.
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Examples
Item qty drops after each sale
You run a running shop. On June 4 the trail-running shoe item in QuickBooks Online (or Xero) shows 18 pairs on hand at $72 cost, $1,296. That afternoon you ring a walk-in sale of 2 pairs at $158 each; the item quantity drops from 18 to 16, Inventory falls $144, and cost of sales rises $144. Open that item and you are looking at perpetual inventory: a detailed record of units and dollars that stays in continuous agreement with stock and can serve as the Inventory subsidiary ledger. Watch the item quantity and the Inventory dollar balance after each sale; do not wait for a count to know what the books say is on hand.
Expense all year, count in December
You run a kitchenware shop. All year you code every bill from a cookware supplier to supplies expense when it arrives and never touch an item quantity. On December 31 you count the shelves, get $8,400 of unsold pans, and post one Inventory asset. That is periodic: purchases hit expense, and cost of sales waits for the year-end physical inventory; it is not perpetual inventory. If the books stay silent until the count, do not call that perpetual; perpetual would have kept quantity and dollars on each SKU after every receipt and every sale.
Why it matters
Perpetual inventory is the running book record that keeps both units and dollars in continuous agreement with stock that should still be on hand. If you track inventory items, this record updates every time you receive goods and every time you sell them, and it can serve as the inventory subsidiary ledger behind the balance-sheet total. You will not take a physical inventory most months (that count is a separate check), and merchandise inventory is only the list of goods you hold to resell. Expense purchases as they arrive and only count at year-end and you are on a periodic system: the books do not stay in agreement with stock, and the P&L cannot tell you cost of sales until you count.
Further reading
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What is Perpetual Inventory in bookkeeping?
A book inventory kept in continuous agreement with stock on hand by means of a detailed record that may also serve as a subsidiary ledger where dollar amounts as well as physical quantities are maintained.
When should I use Perpetual Inventory?
Use Perpetual Inventory when the transaction facts match its definition and you need the ledger and financial statements to reflect the correct account and period.
What is a common mistake with Perpetual Inventory?
Perpetual Inventory is used for perpetual inventory entries, while Paid-In Surplus covers a related but distinct bookkeeping purpose. Review both terms before posting unusual transactions. A common mistake is applying it by label only instead of checking the underlying transaction details.