Credit Notes & Refunds: How to Correct an Invoice

Mistakes happen: a wrong price, a returned item, a cancelled order, a discount agreed after the fact. Once an invoice has been sent, the correct fix is almost never to edit it. Instead, you issue a credit note (called a credit memo in the US and an adjustment note under Australian GST). This guide explains when you need one, what to put on it, and how it affects tax and refunds.

What is a credit note?

A credit note is a document issued by a seller that reduces or cancels the amount owed on an earlier invoice. It’s essentially a negative invoice: it references the original, states what’s being credited and why, and adjusts the tax accordingly.

Why not just edit the invoice?

Once an invoice is issued, it’s part of your accounting records — and your client’s. They may already have entered it, approved it or reclaimed the VAT on it. If you change it and resend it under the same number, the two sets of books no longer match, and an auditor will see an invoice that was silently altered. In VAT systems, corrections are generally expected to be made by a document that refers to the original invoice; that’s what a credit note does.

The rule of thumb: if an invoice hasn’t been sent to anyone, you can still fix it (or void it and record why). Once it’s been sent, correct it with a credit note.

When to issue a credit note

• Pricing or quantity error: you overcharged.
• Returned goods: the customer sent some or all items back.
• Cancelled order or service: the work didn’t go ahead after invoicing.
• Post-invoice discount or goodwill gesture: you agreed to reduce the price.
• Damaged goods or service issue: partial credit as compensation.
• Wrong client details: e.g. invoice issued to the wrong legal entity. Fully credit the original and issue a new invoice to the correct entity.
• Wrong tax treatment: e.g. VAT charged when the reverse charge should have applied.

If you undercharged, you usually issue an additional invoice (or a debit note, in some countries) for the difference rather than a credit note.

What a credit note should include

• The title “Credit Note” (or “Credit Memo”, “Adjustment Note” as appropriate)
• A unique credit-note number (e.g. CN-2026-0004) — see invoice numbering
• The issue date
• Your details and tax number, and the client’s details — the same as on the original invoice
• A clear reference to the original invoice (number and date)
• The reason for the credit
• Description, quantities and amounts being credited
• The tax rate and the tax amount being credited
• The total credit
• What happens next: refund, credit to the client’s account, or offset against another invoice

EU VAT rules treat a document that amends an invoice as an invoice in its own right, and it must refer specifically and unambiguously to the original. The UK, Australia and most other VAT/GST systems have similar requirements.

Example: partial credit for an overcharge

Original invoice INV-2026-0050 (3 Oct 2026):

The client actually booked one full day priced at €800, not two half-days. You issue:

Credit note CN-2026-0004 (28 Oct 2026) — Re: invoice INV-2026-0050 of 3 Oct 2026. Reason: pricing correction — one full-day session at €800 agreed, not two half-day sessions.

Net effect: the client owes €968.00 (€800 + €168 VAT). If they’ve already paid €1,210, you refund €242 or carry it forward as a credit.

Example: full cancellation and reissue

You invoiced the wrong legal entity:

1. CN-2026-0005 credits INV-2026-0061 in full (all lines, all tax), reason: “Issued to incorrect entity.”
2. INV-2026-0066 is issued to the correct entity with the same line items.

Both documents reference each other in their notes, so anyone reading them can follow the trail.

Credit notes and refunds

A credit note is an accounting document; a refund is a payment. They often go together but aren’t the same:

When you pay a refund, keep the payment record with the credit note. If the client needs confirmation, you can send a short note or a document stating the refund amount, date and method — see invoice vs. receipt for how payment confirmations work.

Tax effects

• VAT/GST: the credit note reduces your output tax in the period it’s issued (or as your local rules specify). Your business customer must reduce the input tax they reclaimed. Use the same rate as the original invoice. See how to charge VAT on invoices.
• US sales tax: if you refund a taxable sale, you can generally reduce the sales tax you owe by the tax refunded, following your state’s rules. See sales tax on invoices in the US.
• E-invoicing countries: where e-invoicing is mandatory, credit notes generally must be issued through the same e-invoicing system. See what is an e-invoice.
• Time limits: some countries limit how long after the original invoice a tax adjustment can be made.

Common mistakes

• Deleting or overwriting the original invoice. Keep it; the credit note sits alongside it.
• Not referencing the original invoice number.
• Crediting the net amount but forgetting the tax.
• Using a different tax rate from the original.
• Issuing a credit note without a reason.
• Refunding without a credit note, leaving the books showing income you no longer have.

Quick process

1. Confirm what needs correcting and agree it with the client.
2. Create a credit note referencing the original invoice and stating the reason.
3. Credit the right lines and the matching tax.
4. Send it to the same contact who received the original.
5. Refund, hold as credit, or offset — as agreed.
6. If needed, issue a new, correct invoice with a new number from the invoice generator.

Credit note requirements and tax adjustment rules differ between countries. This guide is general information, not legal or tax advice.