Bookkeeping

Made a mistake on an invoice? How to fix it with a credit note

Why you should not edit or delete an invoice you have sent, when to cancel and reissue, and when a credit note is the right fix.

2 Oct 2026 · 6 min read

An invoice for £2,400 should have been £2,000. A credit note for £400 refers to it, and the invoice now asks for the right amount.

You sent the invoice, and then you saw it: the wrong price, the wrong quantity, or a discount you promised and forgot. The tempting fix is to open the invoice, change the number and send it again. Once an invoice has been sent, that is the one thing not to do. Here is why, and what to do instead.

Why you should not edit or delete a sent invoice

An invoice is a record of a sale, for you, for your customer and for the tax office. Once it has gone out, your customer may already have entered it in their books or claimed back the tax on it. If you change it quietly, your copy and theirs no longer agree. If you delete it, there is a gap in your invoice numbers, and in many countries invoice numbers must run in an unbroken series that you can explain.

So the rule most tax offices expect is simple: a sent invoice stays as it was. You correct it with a new document that points back to it. Our checklist on what every invoice must show explains why numbering matters.

Which fix to use

Three kinds of mistake, three fixes. The more the invoice has been used, the more you fix it with a new document instead of changing the old one.

Still a draft: just edit it

If the invoice has not been issued or sent, it is not a record yet. Change whatever you like, or delete it. Nobody else has seen it.

Sent, but wrong from the start: cancel and reissue

If the whole invoice is wrong, like the wrong customer, the wrong company name or the wrong tax, and nothing has been paid on it, cancel it and issue a fresh one. The cancelled invoice keeps its number and is marked as cancelled, so your series has no gap. Tell your customer which invoice to ignore and which one replaces it.

The sale changed, or you billed too much: a credit note

A credit note is the right fix when the invoice was right at the time, or mostly right, but the amount owed has to come down. For example:

A wrong price or quantity. You billed 12 pages and agreed 10.
Goods returned. The customer sends back one item out of four.
A discount after the sale. A late delivery, a volume rebate, or a goodwill gesture.
A small amount you agree to write off, like bank fees on a payment from abroad.

The credit note takes that amount off the original invoice. If the customer has not paid yet, they pay less. If they have already paid in full, you either refund the difference or keep it as credit for their next invoice, whichever you agree with them.

What a credit note must show

The exact rules depend on your country, but a credit note usually needs:

the words “Credit note” at the top;
its own number, from its own series, and the date it was issued;
your details and your customer's, as on the invoice;
the number and date of the invoice it corrects;
the reason, in plain words;
the amount taken off, and the tax taken off with it, shown separately.

A customer in Sydney returns one of four chairs after paying for three. The credit note takes off the chair and its GST, and the invoice is paid.

How the tax is adjusted

When the amount of a sale comes down, the tax on it comes down too. A credit note reverses the VAT, GST or sales tax on the amount it takes off, at the same rate as the original invoice. You report the lower tax in the period you issue the credit note, and your customer reduces the tax they claimed back. That is why the credit note has to name the original invoice: both sides need to match it up.

In India, a GST credit note must refer to the original invoice and is reported in your GSTR-1. There is a time limit: as the rules stand, a credit note for a sale in one financial year must be declared by 30 November after that year ends, or by your annual return if you file it earlier. After that, the tax cannot be reduced through the credit note. In the UK and the EU, VAT credit notes follow similar rules, and some countries call them corrective invoices. Rules change and depend on your case, so check the details with your accountant.

Good to knowThe opposite exists too. If you billed too little, you can issue a debit note for the extra amount, or simply send a new invoice for the difference. Many businesses find the second easier, and so do their customers.

Before you issue one: talk to the customer

A credit note should never be a surprise. Agree the change first, by message or email, then send the credit note with a short line: “As agreed, here is credit note CN/2026/0003 for £400.00 against invoice OG/2026/0051. The amount still due is now £2,000.00.” If a payment came in short and you are not sure why, read why your client paid less before deciding whether a credit note is the answer.

In Openn InvoiceDrafts can be changed or deleted. An issued invoice can be cancelled while no payment is recorded on it, and it keeps its number. A credit note is made against an issued invoice: it goes to the same customer, uses that invoice's currency, has its own CN series and a reason, and can't be more than what is still owed on the invoice. Once issued, it lowers the invoice's balance, so the status moves to Part paid or Paid by itself.

The short version

Never edit or delete an invoice once it has been sent. Fix it with a new document that points back to it.
Still a draft: edit or delete it.
Wrong from the start and unpaid: cancel it, keep its number, and issue a new one.
Too much billed, goods returned or a discount after the sale: issue a credit note.
A credit note has its own number, the original invoice number, a reason, and the amount and tax taken off.
The tax goes down with the amount. In India, mind the 30 November time limit.
Agree the change with your customer before you send it.