You added up an invoice and the total does not match. Before you reach for the phone, take a breath: this is common and it is usually easy to fix if you handle it in the right order.

Step 1: Make sure you are right

Check your own work before you challenge anyone. Recalculate each line (quantity × unit price), add the lines, apply any discount and then the tax. If you would rather not do it by hand, upload the PDF to InvoiceInspect, which is free. It shows which check failed, the amount it expected, the amount printed on the invoice and the page it found it on.

If a value was hard to read, for example on a scan, the tool marks it as "could not verify" and asks you to confirm it rather than guessing. Always glance at the original page before you write to the supplier.

Step 2: Work out the size of the problem

Write down:

  • which figure is wrong (a line, the subtotal, the tax or the total)
  • what it should be
  • the difference

An overcharge of £250.00 on one line is a different conversation from a one-penny rounding difference. Our guide on calculating VAT on an invoice explains why a penny can be rounding rather than a mistake.

Step 3: Do not pay the difference and move on

It is tempting to pay what you think is the right amount and ignore the rest. Avoid that, for three reasons:

  1. The supplier's records will still show an unpaid balance, which may trigger reminders or late fees.
  2. Your own records will not match the invoice, which makes the audit trail harder to follow.
  3. If you overpay and plan to "fix it next time", you are effectively giving the supplier an interest-free loan.

Step 4: Ask for a corrected invoice or a credit note

There are two usual ways to fix an invoice:

  • A corrected invoice replaces the wrong one. The old invoice is cancelled and the new one carries the right figures.
  • A credit note reduces the amount owed. It is often used when the original invoice has already been recorded or paid.

Which one applies depends on your supplier's process and on local accounting rules, so ask which they prefer. Do not edit the PDF yourself.

Step 5: Send a short, clear email

Keep it factual and give the supplier everything they need to fix it without a call.

Subject: Invoice [number], request for correction

Hello [name],

Thank you for invoice [number] dated [date]. While checking it, I found a calculation difference:

  • Line [x]: [quantity] × [unit price] = [correct amount], but the invoice shows [printed amount].
  • As a result, the subtotal, tax and total are each [higher/lower] than they should be. The total due should be [correct total], not [printed total], a difference of [amount].

Could you please send a corrected invoice or a credit note for the difference? I will arrange payment as soon as I receive it.

Kind regards, [your name]

Step 6: Keep a record

Save the original invoice, your calculation and the email. If the supplier disagrees, you can show exactly where the figures differ.

Stopping it happening again

If the same supplier keeps sending errors, mention it. Often a template or a spreadsheet formula is wrong and one fix removes the problem for every future invoice. And if you check invoices regularly, a quick upload to an invoice checker before approval catches mistakes while they are still easy to correct. For a full manual routine, use our invoice error checklist.