Periodic inventory system

Under a periodic system, the ledger does not continuously assign inventory cost to each sale. Purchases accumulate, the entity establishes ending owned units, and the close derives cost of goods sold:

Beginning inventory + net purchases − ending inventory = cost of goods sold

That equation is only as sound as the count, rights, cutoff, returns, freight, discounts, and cost pool behind it. A periodic system changes the timing of records; it does not relax the evidence needed for existence or ownership.

The close needs separate unit and cost schedules. Start the unit schedule with opening quantity. Add supported receipts, remove supported returns and other known movements, and compare the result with the owned count. For the cost schedule, combine beginning inventory with net purchases and subtract the cost assigned to supported ending units. This residual is cost of goods sold. A journal entry closes purchase-related temporary accounts and establishes the ending inventory balance under the entity's account design.

A periodic residual does not identify why units are missing. Theft, damage, unrecorded sales, cutoff errors, consignment errors, and unit-conversion errors can all affect the result. Investigate those causes through independent records even when the system cannot isolate them from ordinary cost of goods sold.

When judging a cost system, ASC 330-10-30-8 calls for adequate procedures, sound principles, and consistent use. Paragraph 30-9 instead addresses cost-flow assumptions. Record timing and cost assignment remain separate choices.

Use the Cedar Trail worked control before completing the Northstar close.