Invoice Exceptions in Accounts Payable: 8 Types and How to Fix Them
An invoice exception is any invoice that can't move straight to approval and payment because something is missing or doesn't match. The eight most common are incomplete invoices, missing purchase orders, price mismatches, quantity or receipt mismatches, possible duplicates, vendor master issues, bank-detail change requests, and tax discrepancies. Fixing them takes clear match tolerances, a named owner for each exception type, and a queue worked every day.
Key takeaways
- Exceptions are where AP time actually goes. Ardent Partners' 2026 research found only 31.4% of invoices are processed touchlessly at typical organizations, versus 55.2% at best-in-class teams.
- Most exceptions fall into eight predictable types, and each has a different owner and fix.
- Written match tolerances stop small, immaterial differences from becoming exceptions in the first place.
- Treat bank-detail change requests as a fraud-control exception, never a routine update.
- Track exception rate, aging, and repeat offenders by vendor; the root causes are usually upstream of AP.
What is an invoice exception, and why does it matter?
In a clean AP process, an invoice arrives, is coded, matches its purchase order (PO) and receipt where relevant, gets approved, and is paid on time. An exception is anything that interrupts that flow and needs a person to investigate. Every exception costs time, delays approval, and risks late payment, lost early-payment discounts, and strained vendor relationships. At month-end, unresolved exceptions also mean unrecorded liabilities and a slower close.
The scale of the problem is significant. In Ardent Partners' 2026 AP benchmark, best-in-class teams process 55.2% of invoices without manual intervention, while all other organizations manage only 31.4%. For a typical team, that means most invoices need at least one touch, and exceptions are a big reason why.
What are the 8 most common invoice exceptions?
1. Incomplete or incorrectly addressed invoices
What it looks like: The invoice is missing an invoice number, date, PO reference, or remittance details, or it's billed to the wrong legal entity or an old address.
How to resolve it: Return it to the vendor with a specific request for what's missing. Don't fill gaps by guessing, especially the invoice number, which your duplicate checks depend on.
How to prevent it: Send vendors a short invoice requirements sheet during onboarding and include your PO number on every order.
2. Missing purchase order
What it looks like: An invoice arrives for spend that your policy says needs a PO, but there isn't one, or the PO number on the invoice doesn't exist.
How to resolve it: Route it to the requester or budget holder to either raise a PO retrospectively, where your policy allows it, or approve the invoice as a non-PO exception with a documented reason.
How to prevent it: Enforce a "no PO, no pay" policy for agreed spend categories, and tell vendors their invoices will be held without a valid PO. Track repeat offenders by department.
3. Price mismatch
What it looks like: The unit price or total on the invoice doesn't match the PO. Common causes are price increases the buyer didn't update in the PO, unapproved freight or fuel surcharges, and discounts that weren't applied.
How to resolve it: If the difference is within your written tolerance, approve it per policy. If not, the buyer or budget holder decides whether to accept the price, amend the PO, or ask the vendor for a credit note.
How to prevent it: Keep contracted prices current in your PO system and agree in advance how freight and surcharges will be billed.
4. Quantity or receipt mismatch
What it looks like: In a three-way match, the invoice quantity doesn't match what was ordered or what was recorded as received. Often the goods arrived but nobody recorded the receipt, or a partial shipment was invoiced in full.
How to resolve it: Ask the receiving team or requester to confirm what actually arrived. Record the receipt if it was missed; hold the invoice or request a credit if goods are short. Our explainer on three-way matching in accounts payable walks through how matching works and where it breaks.
How to prevent it: Make receiving entry part of the delivery process, not an afterthought, and agree with vendors how partial shipments are invoiced.
5. Possible duplicate invoice
What it looks like: Your system flags an invoice with the same vendor, invoice number, or amount as one already entered. Duplicates often arrive because a vendor resends an unpaid invoice, emails it to two addresses, or sends both a paper and PDF copy.
How to resolve it: Compare the two documents line by line before deleting either. A true duplicate is removed and the vendor is told; a legitimate repeat (such as a recurring monthly charge) is approved with a note.
How to prevent it: Use a single AP inbox, run duplicate checks on vendor, invoice number, amount, and date on every invoice, and reconcile vendor statements regularly so resent invoices are explained.
6. Vendor master issues
What it looks like: The vendor isn't set up yet, is set up twice under slightly different names, or is missing a Form W-9.
How to resolve it: Route new vendors through your onboarding process, including W-9 collection and approval, before paying. Merge duplicate vendor records carefully, keeping the history. A missing or incorrect taxpayer identification number (TIN) is more than an admin issue: the IRS requires backup withholding at 24% in certain cases where a payee doesn't provide a correct TIN.
How to prevent it: Collect W-9s before the first payment, block payments to vendors without a completed setup, and review the vendor master for duplicates at least annually.
7. Vendor bank-detail change requests
What it looks like: A vendor, or someone claiming to be one, asks you to update their bank account, often with urgency and a plausible reason.
How to resolve it: Treat every bank change as a high-risk exception. Verify it by calling the vendor on a phone number already in your records, never one supplied in the request, and have someone other than the requester approve the change. This is the classic business email compromise route: in the Association for Financial Professionals' 2026 Payments Fraud and Control Survey, 74% of US organizations reported being targeted by business email compromise in 2025.
How to prevent it: Document the verification procedure, require dual approval for any change, and flag the first payment to new bank details for extra review. With Nacha's fraud-monitoring rules now applying to all non-consumer ACH originators, a documented, risk-based process for spotting false-pretenses payments is also good evidence for your bank.
8. Sales and use tax discrepancies
What it looks like: The vendor charged sales tax on an exempt purchase, charged the wrong rate, or didn't charge tax on a taxable item, which may mean you owe use tax.
How to resolve it: Ask the vendor to correct tax charged in error, providing an exemption certificate where it applies. For taxable purchases with no tax charged, flag them for use-tax accrual according to your state's rules.
How to prevent it: Keep exemption certificates on file with regular vendors and give your AP team a short guide to which purchase types are taxable. Because sales and use tax rules vary by state, confirm your approach with your tax advisor.
Invoice exceptions at a glance
| Exception | Typical owner | First action |
|---|---|---|
| Incomplete or misaddressed invoice | AP team | Request corrected invoice from vendor |
| Missing PO | Requester or budget holder | Raise PO or approve as documented non-PO spend |
| Price mismatch | Buyer or budget holder | Accept within tolerance, amend PO, or request credit |
| Quantity or receipt mismatch | Receiving team or requester | Confirm receipt; hold or request credit if short |
| Possible duplicate | AP team | Compare documents line by line before acting |
| Vendor master issue | AP lead or controller | Complete onboarding and W-9 before paying |
| Bank-detail change | Controller or designated approver | Independent call-back verification and dual approval |
| Tax discrepancy | AP team with tax advisor input | Request correction or accrue use tax |
How should you set match tolerances?
Match tolerances define how much difference between an invoice and its PO or receipt you'll accept without treating it as an exception. Without them, a few cents of rounding sends invoices into the exception queue; with tolerances that are too loose, overbilling slips through.
Good tolerances are:
- Set and approved by the controller, not decided invoice by invoice.
- Expressed as both a percentage and a dollar cap, so a small percentage on a large invoice doesn't let a large amount through.
- Different by spend type where it makes sense, for example tighter on contracted unit prices and looser on freight.
- Reviewed regularly, using data on how many exceptions each tolerance creates and how much overbilling it catches.
A 6-step invoice exception workflow
- Detect. Flag exceptions as invoices are entered, not at payment time.
- Categorize. Tag each with one of the eight types above so it goes to the right owner.
- Route. Send it to the named owner with the specific question that needs answering.
- Chase. Follow up on a fixed schedule, and escalate exceptions that age past an agreed limit.
- Resolve and document. Record the decision and the reason so auditors and future AP staff can see why.
- Fix the root cause. Review exceptions monthly by type, vendor, and department. If one vendor or team generates most of them, the fix belongs upstream.
Which exception KPIs should you track?
- Exception rate: the share of invoices that need manual intervention.
- Exception aging: how many exceptions are open, and for how long.
- Average resolution time: from flag to resolution, by exception type.
- Repeat exceptions by vendor and department: where the root causes sit.
- Payments affected: late payments or lost discounts traced back to exceptions.
How can outsourcing help with invoice exceptions?
Exceptions are labor-intensive, follow-up-heavy work, which makes them a natural fit for an outsourced AP team. A provider can work the exception queue every day, chase owners on a schedule, document every resolution, and report monthly on root causes, while your team keeps the decisions that need business judgment and the approval of bank changes. With an India-based team, much of that chasing happens overnight, so owners start the day with a clear list of what they need to decide.
For the bigger picture of handing invoice processing to a provider, see our complete guide to invoice processing outsourcing for US businesses. And for how we run the full process, including the exception queue, see our outsourced accounts payable services.
Frequently asked questions
What is an invoice exception in accounts payable?
An invoice exception is any invoice that can't move straight to approval and payment because information is missing or doesn't match, such as a missing PO, a price or quantity mismatch, a possible duplicate, or a vendor setup issue.
What are the most common invoice exceptions?
The most common are incomplete invoices, missing purchase orders, price mismatches, quantity or receipt mismatches, possible duplicates, vendor master issues such as missing W-9s, bank-detail change requests, and sales or use tax discrepancies.
How do you reduce invoice exceptions?
Set written match tolerances, enforce PO policies, keep vendor prices and records current, record receipts promptly, use a single AP inbox with duplicate checks, and review exceptions monthly to fix root causes upstream.
Who should resolve invoice exceptions?
It depends on the type. The AP team handles data and duplicate issues, budget holders resolve PO and price questions, receiving teams confirm quantities, and a controller or designated approver handles bank-detail changes.
Should a vendor bank-detail change be treated as an exception?
Yes. Every bank-detail change should be verified by calling the vendor on a number already on file and approved by someone other than the person who received the request, because it's the most common route for business email compromise fraud.
This article is general information, not tax or legal advice. Backup withholding and sales and use tax rules depend on your situation and state, so review them with a licensed CPA.
Is your exception queue slowing AP down? We can review a month of your exceptions and show you where they come from and how a daily exception workflow would handle them. Talk to our team.