An invoice dispute rarely starts with a customer who refuses to pay. It usually starts with an invoice the customer cannot approve: the PO number is missing, the price does not match, or the goods have not been booked in. Every one of those invoices sits unpaid while someone investigates. The good news is that the same few causes come up again and again, and nearly all of them can be prevented before the invoice goes out.
The most common causes
1. Missing or wrong PO number
Many businesses, especially larger ones, will not pay an invoice that does not quote a valid purchase order number. Their accounts payable team cannot match it to an approved order, so it goes back to the buyer, or into a queue.
Prevent it: Make the PO number a required field before an order can be invoiced. Check whether the customer issues one PO per order or a blanket PO, and when blanket POs expire.
2. Pricing mismatch
The invoice shows a different price from the quote, the contract or the PO. Common reasons include an expired promotional price, a price increase the customer was not told about, or a discount agreed by sales but never set up in the system.
Prevent it: Keep customer price lists in one place, and make sure sales agreements reach the billing team before the first invoice. Give customers written notice of price changes.
3. Quantity or delivery problems
The customer was invoiced for 100 units and received 95. Or the delivery arrived damaged, late or incomplete. Their system will not approve the invoice until the goods received match it.
Prevent it: Invoice from what was actually shipped or delivered, not from what was ordered. Handle short shipments and back orders with separate invoices, or clearly marked partial invoices.
4. Missing proof of delivery
The customer says the goods never arrived, and you cannot show that they did. Without proof, you are stuck.
Prevent it: Capture a signed delivery note, carrier tracking confirmation or a completion sign-off for services, and file it against the invoice so anyone on the team can retrieve it in minutes.
5. Wrong billing entity or address
The invoice is addressed to the parent company when the order came from a subsidiary, or it goes to a site office instead of the central accounts payable address or email. It may never reach the person who can approve it.
Prevent it: Confirm the legal entity, billing address and accounts payable contact on the credit application, and check them again when a customer restructures or moves.
6. Unclear descriptions
“Services rendered” or an internal product code means nothing to the person approving the invoice. They have to ask what it is for, and the clock keeps running.
Prevent it: Describe what was supplied in the customer’s language, with dates, quantities, the project or site name and any reference the customer gave you.
7. Tax errors
The wrong tax rate, tax charged when the customer is exempt, or missing tax registration details. In the UK this is usually VAT; in the US, state and local sales tax; in Canada, GST/HST and, in some provinces, PST or QST. A tax error normally means a credit note (credit memo in the US and Canada) and a reissued invoice, which can add weeks.
Prevent it: Hold exemption certificates and tax registration numbers on the customer record, and review tax settings when you start selling into a new region. Tax rules vary by jurisdiction, so confirm the treatment for your situation with a qualified tax adviser.
A prevention checklist
Run new customers and new invoice types through this list. Most items take seconds once they are part of the routine.
- ☐ Correct legal entity and billing address confirmed at account opening
- ☐ Accounts payable contact name and email on file
- ☐ PO number required and validated before invoicing
- ☐ Prices checked against the current contract or quote
- ☐ Price changes notified to the customer in writing before they apply
- ☐ Invoice based on goods shipped or services completed
- ☐ Proof of delivery or completion captured and filed
- ☐ Descriptions include dates, quantities and the customer’s references
- ☐ Tax rate and exemptions checked for the customer’s location
- ☐ Payment terms and due date shown clearly on the invoice
- ☐ Invoice sent to the right channel (email address, supplier portal or post)
A courtesy reminder a few days before the due date also helps. It gives the customer a chance to raise a problem while there is still time to fix it. Our payment reminder email templates include one you can use.
Keep a dispute log
Some disputes will still get through. A simple log stops them from going quiet and shows you where your process keeps failing. A shared spreadsheet is enough to start.
| Column | What to record |
|---|---|
| Date raised | When the customer first told you |
| Customer | Account name and number |
| Invoice number | One row per invoice |
| Amount disputed | The disputed portion, not always the full invoice |
| Cause | Pick from a fixed list: PO, price, quantity, delivery, POD, billing entity, description, tax, other |
| Owner | The person responsible for resolving it |
| Next action and date | What happens next, and when |
| Status | Open, awaiting customer, awaiting internal, resolved |
| Resolution | Credit note, reissue, proof sent, customer paid |
| Date resolved | So you can measure time to resolve |
Two habits make the log useful. First, chase the undisputed part of any invoice as normal: a dispute over one line should not hold up payment of the rest. Second, review the “cause” column every month. If pricing errors keep coming up, the fix is in your price setup, not in faster dispute handling.
For the resolution side, from first contact to closing a dispute, read how to handle disputes in accounts receivable efficiently. And because disputed invoices sit in receivables until they are settled, cutting disputes is one of the most direct ways to bring your DSO down.
Key takeaways
- Most disputes come from a few avoidable errors: PO numbers, pricing, quantities, proof of delivery, billing details, descriptions and tax.
- Fix the invoice before it goes out. Prevention is cheaper than investigation.
- Use a short checklist for new customers and new invoice types.
- Log every dispute with a cause, an owner and a next action, and keep collecting the undisputed amount.
- Review dispute causes monthly and fix the process behind the most frequent ones.
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