An invoice exception is any bill that can’t go straight from arrival to approved and posted. Something about it needs a person to stop, look, and usually ask someone else a question. The amount doesn’t match what was agreed, the supplier isn’t set up yet, the PDF is a proforma, nobody knows who should approve it.
Ardent Partners’ State of ePayables 2025 puts the exception rate at 20.9% for most organisations (“All Others” in the report) and 11.1% for the top performers it calls Best-in-Class. So at a typical business, roughly one invoice in five takes a detour, and even the best teams still see about one in nine. The same report puts average processing time at 13.5 days for All Others against 2.9 days for Best-in-Class. It’s hard to get anywhere near the faster number while a fifth of your invoices sit in someone’s inbox waiting for an answer.
For a small business the problem feels different from how it does in a large AP department. There’s no exceptions team. The person who handles them is the same person entering bills, chasing approvals, and paying suppliers, and often doing payroll and month-end too. Every exception is an interruption, and the ones that don’t get handled quietly age into late payments, supplier calls and a messy close.
Where exceptions come from when you don’t use purchase orders
Most writing on exceptions assumes a three-way match: purchase order, goods receipt, invoice. If any of the three disagree, you have an exception. Plenty of SMEs don’t raise POs for most of their spend, so their exceptions look different. They tend to fall into a handful of groups.
| What went wrong | Typical cause | Who has to act |
|---|---|---|
| The document isn’t a payable invoice | A proforma, quote, delivery note or statement sent as if it were a bill | Supplier, for the final invoice |
| Key details missing or wrong | Wrong legal entity name, missing tax registration number, no invoice number, unreadable scan | Supplier, for a corrected invoice |
| Amount differs from what was agreed | Old price list, a discount not applied, extra charges nobody approved | Whoever agreed the price, then the supplier |
| Tax looks wrong | VAT charged at the wrong rate, charged when it shouldn’t be, or calculated incorrectly | Supplier, sometimes your accountant |
| Supplier record problem | New supplier not set up, or bank details different from last time | You, and for bank changes, a verification call |
| Possible duplicate | Same invoice sent by email and WhatsApp, or resent as a reminder | You |
| No clear approver or coding | Nobody owns this type of spend, or nobody knows which account it belongs to | You, then a manager |
Two things stand out from that table. First, most exceptions are fixed by someone other than the person who found them. Second, a few causes are entirely preventable with a bit of setup, and a couple you actually want to keep catching.
A simple way to triage
When exceptions pile up, the instinct is to work through them oldest first. That’s fine for clearing a backlog, but it doesn’t help next month. A slightly better habit is to tag each exception with a reason as soon as you spot it, and to sort the pile by who has to act.
Supplier-side problems go back to the supplier the same day with a specific request: “Please reissue this invoice to our registered company name and include your VAT number.” Vague replies like “there’s an issue with your invoice” get vague responses and another week of delay. Internal problems, like a missing approver or a price nobody recognises, go to a named person with a date. Problems you can fix yourself, such as setting up a new supplier or merging a duplicate, get done in one sitting rather than spread across the week.
Keep a short log alongside this. A spreadsheet works: date found, supplier, reason, who it’s waiting on, date resolved. It takes a few seconds per invoice and it does two jobs. It gives you an audit trail of what happened to each disputed bill, and after a month or two it shows you where your exceptions actually come from. In many businesses a small number of suppliers and two or three reasons account for most of the list. That’s where the upstream fixes pay off.
Fixing the causes, not just the invoices
Some exceptions disappear once suppliers know what you need. A one-page note sent to new suppliers, and to the repeat offenders in your log, can cover your exact legal entity name and address, your tax registration number if they need it on the invoice, the name or reference they should quote, the single email address invoices should go to, and one invoice per PDF. It’s not glamorous, but it removes a whole category of “please reissue” emails.
Price disputes usually trace back to agreements that only existed in a phone call. If someone in the business negotiates a rate, it helps to have that rate written down somewhere AP can see it, even if it’s an email forwarded to a shared folder. Without that, the person processing the invoice has no way to tell whether the amount is right.
Approval and coding exceptions come from unclear ownership. A short list that says which person approves which supplier or type of spend, and which account each regular supplier is coded to, solves most of them. It’s worth reviewing that list whenever someone joins or leaves.
Document problems, like proformas and statements being treated as bills, are partly a supplier habit and partly an intake problem. When invoices arrive through several channels (a shared inbox, someone’s personal email, a WhatsApp chat with the supplier, a paper copy on a desk) it’s easy for the wrong document to be entered, or for the same invoice to be entered twice from two channels. Bringing intake into one place, or at least into one review step, cuts both. We covered the duplicate side of this in more detail in our post on duplicate invoice payments.
Some exceptions are the point
It’s tempting to treat the exception rate as something to drive towards zero. Best-in-Class teams in the Ardent report still sit at 11.1%, and that’s healthy. A changed bank account on a supplier invoice should always stop the bill until someone has confirmed the change through a known phone number, because that’s exactly how payment fraud works (warning signs here). A possible duplicate should always get a second look. A tax invoice missing the details you need to reclaim input VAT should be fixed before it’s posted, not discovered at return time.
The goal is to get rid of the exceptions that are just friction, so the ones that matter get proper attention instead of being waved through with everything else.
Measuring it
Two numbers are enough for most small teams. The first is your exception rate: the share of invoices processed in a month that needed some kind of intervention beyond normal review and approval. The second is how long exceptions stay open, from the day you spot the problem to the day the invoice is approved. If you keep the log described above, both fall out of it with a couple of spreadsheet formulas.
You don’t need to hit the Best-in-Class number. What’s useful is seeing your own rate go down over a few months, and seeing which reasons drop off the list after you’ve fixed their cause. For context on what slow processing costs in money terms, our breakdown of AP costs uses the same Ardent report.
Where software fits
Different tools catch different exceptions, and the right one depends on how you buy.
If most of your spend runs through purchase orders and goods receipts, a procurement or AP suite with built-in matching is the natural fit. It can compare invoice lines against the PO and receipt automatically and only surface the mismatches. That works well for businesses that already have the PO discipline, such as distributors or manufacturers buying stock.
If most of your invoices arrive without a PO, from a mix of suppliers and channels, matching has nothing to match against. The useful checks happen earlier: is this a final invoice or a proforma, is this a duplicate, are the bank details the same as last time, are the tax details there, are any fields uncertain. That’s the problem Clearline is built for. It reads invoices from WhatsApp, email or upload, classifies the document type and holds proformas and other non-final documents for confirmation, flags duplicates and changed bank details, and sends only the uncertain fields to a person for review. Nothing posts to your accounting system until it’s been confirmed, and the bill keeps a link to the original email or message it came from.
No tool settles a pricing dispute with a supplier for you. That’s still a conversation. What software can do is make sure the right invoices reach that conversation quickly, with the evidence attached, instead of being found three weeks later.