Paying an invoice is the easy part and the last part, and most of what goes wrong happens before the money moves. The order of the checks matters, because each one is cheap before payment and expensive afterwards. Recovering money paid to the wrong account, or paid twice, or paid for goods that never arrived, is difficult in a way that checking beforehand is not.
Confirm it is genuine and it is yours
The supplier exists in your records, the invoice is addressed to your organisation, and the invoice number has not been seen before. Duplicate detection on the supplier and invoice number catches the accidental case; the deliberate case, an invoice from a supplier you do not use, is caught by the same check plus somebody recognising the name.
Match, then approve
Compare with the purchase order and the goods receipt where they exist, and route anything outside tolerance to whoever can resolve it. Where there is no order, approval falls to whoever authorised the spend, and it should be recorded with the amount and the date. Approval is the point at which the organisation accepts that the money is owed.
Verify the bank details, then pay on terms
Bank detail changes are the highest-value fraud in payables, and the defence is procedural rather than technical: verify a change using contact details you already hold, not those on the request, and record the verification. Then pay on the agreed terms, and send a remittance so the supplier can allocate it without calling you.
Questions people ask about how to pay an invoice
What if we cannot match the invoice?
Do not pay it yet. Route it to whoever can establish what it is for. Paying an unmatched invoice to keep a supplier happy is how organisations pay for goods that never arrived.
How do we avoid paying twice?
Check the supplier and invoice number combination before payment, and be careful with reissued invoices carrying a new number for the same goods, which duplicate detection alone will not catch.
Should we always pay on the due date?
Paying to terms is the default. Paying early has a cost of capital and paying late has a relationship and sometimes a legal cost, so both should be deliberate decisions rather than accidents of process.