Credit and debit notes in New Zealand: supply correction information

If an invoice you've given turns out to charge the wrong amount of GST, you correct it with supply correction information (SCI). In practice that's a credit note when the GST was too high, or a debit note when it was too low.

What a note must show

1. Your name (or trade name) and GST number.
2. The date you give the correction.
3. Details that identify the original invoice, such as its number and date.
4. The correction, including the adjustment to the GST.

Invoice Native links every note to its invoice and prints, under the title, the GST adjustment, the original invoice's number and date and the reason, for example GST adjustment $72.00 · Against Tax Invoice INV-0041 dated 15/09/2026 · Reason: Overcharge.

Credit note or debit note?

In your GST return

Include the adjustment in the GST return for the period in which you gave the note. On the payments basis it changes what each payment counts for; on the invoice basis, a credit note subtracts and a debit note adds.

Make one with the generator

The free New Zealand invoice generator makes credit and debit notes as well as invoices. Signed-in businesses create a note straight from an issued invoice: the client, the lines and the GST treatment are copied, you change what needs changing and choose a reason, and the note is linked to the original.

A worked example

You billed a client $480 plus GST for a year of website hosting on invoice INV-0041, dated 15 September 2026 — $552.00 in all. They cancel before the year starts. You give them a credit note on 3 October showing:

• your name and GST No. 49-091-850;
• the date, 3 October 2026, and the credit note number, say CN-0001;
• "Against Tax Invoice INV-0041 dated 15/09/2026";
• the reason: cancelled order;
• the line for $480.00, the GST adjustment of $72.00 and the total credited of $552.00.

The $72.00 comes off the GST in your return for the period that includes 3 October, even if INV-0041 was in an earlier period.

When you don't need a note

You don't need supply correction information for a prompt-payment discount or a rebate if its terms were agreed in writing beforehand or set out on the original invoice. You also don't need one when nothing about the GST changes — a correction to a typo in the description can be agreed with your client without a note.

Corrections that aren't about price

The rules also cover an invoice that named the wrong party, had the wrong date or described the supply wrongly. Give a credit note for the wrong invoice and a new invoice with the right details, so your records and your client's line up.

If you're not registered for GST

A business that isn't registered for GST charges no GST, so there's no GST to correct. You can still give a credit note for a return or an overcharge; it simply shows no GST. Invoice Native titles it "Credit Note" without a GST number.

On the payments basis

If you account for GST on the payments basis, a sale counts when you're paid. A credit note given before your client pays reduces what they owe, so the GST on each payment is worked out on the corrected amount. A credit note given after they've paid in full usually means a refund: the GST on the refund comes off in the period you give the note.

Invoice Native's GST101A summary handles both: notes count in the period they're given on the invoice basis, and on the payments basis each payment counts its share after the notes issued on its invoice by the day it was paid.

Numbering and records

Give each credit and debit note its own number, separate from your invoices — for example CN-0001 and DN-0001 — and keep a copy for 7 years. Never delete or edit an invoice once you've given it to your client: correct it with a note, so your records show what happened and when.