An invoice can differ from a purchase order for several reasons: an approved price change, a partial shipment, a substitute, freight, a billing error or a change that nobody authorized. The mismatch is a question to investigate, not an instruction to edit the PO until it matches the bill.
Start with the original request, the buyer-approved changes and the physical receipt. Keep all three visible alongside the invoice.
Identify the kind of difference
| Difference | Check first | Owner of the next decision |
|---|---|---|
| Price | Original price, supplier proposal and approval | Authorized buyer or finance reviewer |
| Quantity | Ordered, received, still due and previously billed | Receiver and buyer, with AP checking billing |
| Substitute | Actual item, pack conversion, suitability and acceptance | Buyer and relevant kitchen/quality owner |
| Freight or surcharge | Agreed charge and allocation, including other invoices | Buyer and finance |
| Credit | Credit requested, issued and applied | Buyer follows up; finance verifies posting |
| Duplicate | Supplier, invoice identity, amount and prior entries | AP |
An invoice proves what the supplier is asking to be paid. It does not prove that goods arrived or that a proposed change was accepted.
A worked mismatch
The following is illustrative. A buyer orders ten cases at $40 each: $400 before tax or freight. The supplier proposes $42 per case and says eight cases can arrive this week, with two later. The buyer accepts the price and split delivery.
The first receipt is seven cases. The invoice is for eight cases at $42: $336.
The reviewer should see:
- Original order: ten cases at $40.
- Approved order: ten cases at $42, split delivery expected.
- Physical receipt: seven cases.
- Invoice: eight cases at $42.
- Difference to resolve: one billed case not recorded as received, plus the remaining delivery commitments.
The seven received cases have a goods value of $294. The $42 difference needs resolution under the agreement; it is not automatically a loss, a valid payable or an issued credit. Confirm whether a receipt was missed, the supplier billed ahead under agreed terms, a replacement is due or a credit is required.
Do not receive the missing case just to make the documents agree. Do not reduce the original order without recording whether the remaining quantity was cancelled.
Preserve approved changes as they happen
A living purchase order can keep supplier correspondence, revisions and receipts together. LineNow can extract supported supplier messages into order context, reducing re-entry. The buyer still controls commercial acceptance and the receiver confirms the physical result.
When a supplier proposes a different pack or ingredient, check identity, units and suitability before acceptance. An apparent one-for-one substitution can change unit cost, recipe yield or product requirements.
See how supplier email processing works for ambiguous replies and matching limitations. Confirm each actual supplier channel during setup; no system should be assumed to read every portal or private message automatically.
Keep AP's control intact
Earlier review complements three-way matching. AP still checks authorization, receipt evidence, coding, tax, duplicate invoices, payment terms and unresolved differences. Updating the order earlier gives that review better evidence; it does not guarantee the next invoice will match.
An invoice OCR tool can help capture the bill. A supplier-message workflow can help preserve changes before it arrives. Either may be useful, and both can coexist. Evaluate the missing handoff rather than treating these controls as competing alternatives.
Measure the actual work
Review a comparable sample of invoices. Record which differences were valid, which required correction, how many remained open and active minutes spent resolving them. Count only verified overpayments or recovered credits as dollar outcomes; track review-time capacity separately.
There is no supported universal percentage of COGS lost to mismatches. Build your own baseline with the procurement time audit and ROI worksheet.
Use PO status tracking to evaluate whether the buyer, receiving shift and bookkeeper can explain the same changed order without reconstructing its history.