INVENTORY CONTROL & SYSTEMS
Perpetual
inventory
Perpetual inventory is a method of maintaining inventory balances by recording stock transactions as they occur. Receipts, shipments and authorized adjustments update the recorded quantity rather than waiting for a periodic stocktake to calculate it.
EVERY MOVEMENT SHOULD LEAVE A RECORD
- ReceiveRecord the item, quantity, unit and destination.
- Move or shipRecord transfers and stock leaving the operation.
- Verify & reconcileCount physical stock, investigate differences and approve adjustments.
Perpetual records describe what the system knows. Counts check what is physically there.
ONE SKU. A RUNNING BALANCE.
100 at the start.
113 after the events.
Begin with 100 eaches. Receive 40, ship 25 and post an approved adjustment removing two damaged units.
100 + 40 − 25 − 2 = 113 eaches
Moving five units from one bin to another changes the location balances, but not the facility total. Allocating an order can reduce available stock without reducing physical on-hand stock.
Keep those statuses separate so “on hand,” “available” and “sellable” are not treated as interchangeable.
| Event | Change | Recorded balance |
|---|---|---|
| Opening balance | — | 100 |
| Receipt | +40 | 140 |
| Shipment | −25 | 115 |
| Approved damage adjustment | −2 | 113 |
Perpetual records and physical counts work together
A cycle count tests selected items or locations against the system record. If the ledger says 113 and a controlled count finds 111, investigate receipts, picks, transfers, unit conversions and adjustment history before accepting a change.
A physical count does not explain the cause on its own. Record the reason, evidence and reviewer for an approved correction. Repeated differences in the same process need a process fix as well as a balance correction.
| Approach | How balances are maintained | Physical verification |
|---|---|---|
| Perpetual inventory | Transactions update the running record | Counts test and reconcile that record |
| Periodic inventory | Balances are established at defined counting intervals | Counts are central to determining the period-end quantity |
A WMS can support perpetual records, but delayed integrations or offline work can delay updates. Ask which events trigger updates and how failed transactions are detected.
WHAT THIS MEANS FOR YOUR QUOTE
Include the work that keeps records credible
Clarify who pays for routine cycle counts, exception investigations, recounts and stock adjustments. Ask how returns, quarantined stock and damaged units are reported.
A stock discrepancy allowance and a counting service are different contract questions. Define both rather than assuming one answers the other.
Put this term to work. Use the 3PL selection guide to turn these operating requirements into provider checks, and the 3PL RFP guide to document evidence, responsibilities and exceptions.
Protect the running balance
- Record the correct unit. A case entered as an each creates an error even when the transaction posts immediately.
- Reconcile interfaces as well as stock. A successful warehouse transaction may still fail to reach the sales channel or ERP.
- Keep an audit trail. Preserve transaction references and review evidence for adjustments.
A LITTLE MORE CONTEXT
Questions about Perpetual Inventory
Does perpetual inventory remove the need for counting?
No. Counts verify the physical stock and help detect errors in the running record. The appropriate counting program depends on the operation and its requirements.
Is perpetual inventory always real time?
It is intended to update with transactions, but practical visibility depends on when work is recorded and how integrations operate.
Does a bin transfer change total on-hand inventory?
A correctly recorded transfer within the same facility changes location balances, not the facility total. Transfers between facilities need matching transaction and in-transit rules.
Source & example notes
Oracle Inventory User’s Guide: cycle counting. Explains physical verification and approval options for inventory differences. The running ledger above is a 3PL Hub example.
Examples are illustrative. Confirm operational definitions, service scope and charges with your provider.
Last updated: · 3PL Hub
