Glossary
What is perpetual inventory?
Perpetual inventory is a method where stock records update continuously with every receipt, sale, transfer, and adjustment, so the system always shows a current count.
Definition
Under a perpetual system, every movement writes to the record the moment it happens. Receive 40 units, the count goes up 40. Sell 3, it drops 3. Transfer 5 to a truck, the warehouse count drops and the truck count rises. At any moment, the system can answer what should be on the shelf, and the running record doubles as an audit trail of who moved what, when.
The alternative is periodic inventory, where the count is only known after a physical count and everything between counts is a guess. Perpetual is the standard for any operation that needs to promise stock to customers, trigger reorders automatically, or trace a variance back to its cause.
The honest caveat: perpetual records drift. Scans get skipped, damage goes unrecorded, a case pack gets received as a single unit. A perpetual system tells you what should be there, and cycle counts verify what actually is. The two work together: continuous records catch most movement, periodic counting catches the leaks. Teams that run perpetual records without ever counting end up with precise-looking numbers that are quietly wrong, which is more dangerous than knowing you don't know.
Example
A field service company scans every part onto and off its 12 trucks. At 2pm on a Tuesday, dispatch can see truck 7 carries 4 of the needed valve without calling the technician, because the morning's two installs already decremented the truck's count.
By Cameron Priest · Co-founder, Order3
Cameron Priest builds inventory and order management software for people who run physical stock.
Updated 2026-06-16
Where this lives in Order3