Short answer: invoice reconciliation is checking each invoice against an independent record of the same transaction and explaining every difference. Before payment you check it against the order and what was received. After payment you check it against the bank. At month end you check it against the supplier's statement. Software, including AI invoice reconciliation software, can do most of the matching; a person should still decide what to do about the differences.
What does invoice reconciliation actually compare?
The phrase is used for three different checks. They happen at different points and catch different problems.
| Check | Compared with | When | What it catches |
|---|---|---|---|
| Invoice to order and receipt | Purchase order and delivery note or goods receipt | Before the invoice is approved for payment | Wrong prices, short deliveries, items never ordered |
| Invoice to payment | Bank statement lines | When the bank is reconciled | Unpaid invoices, short or over payments, one payment covering several invoices |
| Invoice to supplier statement | The supplier's statement of account | Monthly or quarterly | Missing invoices, duplicates, unposted credit notes, typing errors |
The first is usually called two-way or three-way matching, and we cover it in detail in three-way matching. The third has its own guide: supplier statement reconciliation. This post covers how the three fit together, with the most attention on the middle one, because it is the one most small businesses and bookkeeping clients do every week.
Why reconcile invoices at all?
- To pay only what is owed. A duplicate bill or a keyed-in €1,540 that should have been €1,450 is cheap to fix before payment and awkward after it.
- To know what is really outstanding. Aged payables and receivables reports are only useful if paid invoices are marked paid and partly paid invoices show the right balance.
- To keep VAT right. In the UK, HMRC says you can only reclaim VAT on a valid VAT invoice, not on a statement or a delivery note, and if you pay less than the invoice amount you can only reclaim VAT on the amount you paid. A short payment is a VAT question as well as a cash one.
- To keep the records you need. HMRC also requires purchase and sales invoices, credit and debit notes and bank statements to be kept for at least six years. Reconciling is how you find out one is missing while you can still ask for a copy.
How to reconcile invoices against payments, step by step
- Fix the period. Take the bank statement for the period and run the open invoices (or open bills) report to the same date.
- Clear the exact matches. Same amount, same counterparty, invoice number in the reference. Most accounting software suggests these for you. When you match a payment to an invoice, the software marks it paid and records the payment; QuickBooks, for example, warns that matching to the wrong open invoice affects your reports, so confirm before you accept.
- Work the combined payments. One transfer that pays several invoices is the most common reason a line will not match. Look for the set of open invoices from that counterparty whose total equals the payment. We walk through this in one payment, many invoices.
- Look at the near misses. A payment a few euros short is often a bank charge, an early payment discount or a deduction for a disputed line. Check the remittance advice or ask.
- Decide each difference. Book the bank charge, raise a credit note for the agreed discount, or leave the balance open and chase it. Never write a difference off just to clear the line.
- Check what is left on both sides. Invoices still open after their due date and payments with no invoice behind them both need an answer. A payment with no invoice often means the invoice never reached the books.
- Record who approved what. Each match and each adjustment should show who made it and when, so the next person (or the reviewer at year end) can follow it.
A worked example
A wholesale client receives a transfer of €4,860.00 on 15 October from a restaurant customer. The reference says "OCT PAYMENT". The customer has four open invoices:
| Invoice | Date | Amount |
|---|---|---|
| 2207 | 2 Sep | €1,845.00 |
| 2215 | 9 Sep | €2,214.00 |
| 2231 | 23 Sep | €816.00 |
| 2240 | 7 Oct | €1,230.00 |
No single invoice matches. Invoices 2207, 2215 and 2231 total €4,875.00, €15.00 more than was received. The remittance confirms those three invoices and says the customer's bank deducted a €15.00 transfer fee.
The bookkeeper:
- matches the €4,860.00 to invoices 2207, 2215 and 2231;
- books the €15.00 as a bank charge, as the client's policy allows for small fees, instead of leaving three invoices partly open;
- leaves invoice 2240 open, as it is not yet due.
Without the remittance, the most likely combination would still have been the three oldest invoices, but that is a guess. Good software makes the same guess, shows it as uncertain and waits for someone to confirm it.
Where AI, machine learning and "GPT" fit
Vendors describe invoice reconciliation software as AI, ML, generative AI or GPT-based. Under the labels, three different things are going on:
- Reading documents. Turning PDFs, scans and phone photos of invoices and statements into structured data. Modern language models are good at this, including the vague payment references above.
- Learning from history. Machine learning that notices this customer always pays monthly in one transfer, or that this supplier's invoice numbers appear without the prefix in the bank reference.
- Searching combinations. Working out which set of open invoices adds up to a payment, allowing for small differences. This is closer to arithmetic than to AI, but it is where most of the time goes when it is done by hand.
Whatever the label, ask the same questions: does it read your clients' actual documents, does it explain each match, does it show how sure it is, and does it wait for approval before anything is posted? The AI reconciliation software buyer's guide has a full checklist and the red flags.
Fix the invoices and the reconciliation gets shorter
Most differences in invoice reconciliation are created when the invoice is entered: a typo in the amount, the same bill booked twice, a bill posted to the wrong supplier. ACCA lists the same errors behind supplier statement differences: invoices on the wrong account, credit notes not processed and figures transposed when an invoice is entered. Checking each invoice when it arrives, and catching duplicates before they are booked (see how to detect and prevent duplicate invoices), removes most of them before any reconciliation starts.
Where Invoreg fits
Invoreg works on two of the three checks. It reads every supplier invoice, including scans and phone photos, line by line, flags duplicates against the workspace and the bills already in your accounting software, and registers the bill only after a person approves it. Its bank reconciliation reads bank statements, including PDFs and scans, matches payments to invoices, including one payment for several invoices, flags the matches it is unsure of and marks matched invoices paid once you approve.
It does not hold purchase orders or goods receipts, so three-way matching stays in your purchasing system, and it does not reconcile supplier statements itself. If invoice-to-payment matching is where your week goes, try it on your own invoices: the first 20 invoices are free.