Perpetual inventory
Perpetual inventory means stock levels update with every movement in and out, so the system always holds a current figure. The alternative, periodic inventory, only knows the true position when somebody counts it.
Also searched as: continuous stock, perpetual vs periodic inventory
Updated July 2026
Periodic counting is not wrong, it is just slow to tell you anything. Between counts you are trading on a number that drifts, and the longer the gap the more it drifts. Shrinkage, breakage and mis-picks all accumulate silently.
Perpetual inventory does not remove the need to count. Physical counts still happen, but they become a check on a number you already have rather than the only source of it, and the variance they reveal is small enough to investigate.
The honest caveat: perpetual only works if the movements are actually recorded. A system that says 40 units while someone is taking stock out of the back door without scanning it is confidently wrong, which is worse than being unsure.
What a count should look like
In a business running perpetual inventory with barcode picking, a cycle count typically finds variances in the low single digits as a percentage. If a count finds 20% variance, the problem is process discipline, not software.
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