How to Amend an Invoice: Fixing Errors With a Credit Note

28/08/2026InvoicesIssue & Manage Invoices
Share on:
How to Amend an Invoice: Fixing Errors With a Credit Note
Spotted a mistake on an invoice? How you fix it depends on one thing: whether it's still sitting in your account or your customer already has it. While it's a draft, a change takes seconds. Once it's been sent, you'll usually put things right with a credit note rather than editing the original.

While it's still a draft, change whatever you like

An invoice you haven't sent anywhere yet is just a working document. Change the line items, figures, customer details and dates as much as you like — or scrap it and start again. Nothing formal is needed while the invoice is neither sent nor entered in your books.

Box illustration
Before you send, run a quick eye over the things that go wrong most often: the client’s details and VAT number, the invoice number, the figures (net, VAT rate and total), and the payment terms. Catching it now is far easier than sorting it out later.

Once it's with your customer, HMRC rules apply

As soon as you send an invoice, it stops being only yours. Your customer may have entered it in their accounts, and if you've recorded it too, it's part of your own books. From here on, you don't fix an invoice by rewriting it.

Box illustration
Never delete or write over an invoice you’ve already sent and recorded. HMRC expects a clear audit trail, so the original and its correction need to sit side by side in your records — keep both for at least six years. Quietly changing a sent invoice leaves your books and your customer’s out of step.

Instead, you correct the record with a separate document:

  • Credit note: reduces or cancels the amount on the original invoice — for returns, an overcharge, or a discount agreed after the fact.

  • Debit note: increases the amount, for example when something was left off or a price went up.

  • Re-issued (corrected) invoice: replaces the original — best when it hasn't really entered circulation yet.

If you're VAT-registered, the credit note has to handle the VAT too. Per HMRC, issue it within 14 days of the price change or refund, credit the VAT in the same proportion as the original invoice, and adjust the VAT on your return for the period in which you issue the credit note.

A VAT credit note must carry its own unique number (kept separate from your sales invoice numbering), the date, and a clear reference to the original invoice — plus the VAT being credited. Miss those details and HMRC may not accept it as a valid VAT adjustment.
Box illustration
Priya, a florist, invoiced a client £360 for an event order — £300 plus £60 VAT at 20%. The client later returned £60 of stock. Priya left the original invoice untouched and raised a credit note for £72 (£60 net plus £12 VAT), referencing the original invoice number with the reason „returned goods“. Her VAT return for that period reflects the £12 reduction.

Amending an invoice in MyInvoiceOnline

In the app, the steps follow the same logic — what you do depends on the state the invoice is in.

A draft invoice

An invoice you haven't issued yet, you simply open and edit as needed.

A draft invoice edit preview

An invoice you've already issued

Editing an invoice after you've issued it is part of the Premium plan (and it works during your free trial). On the Mini plan, an issued invoice is view-only — you can't change it after the fact.

To correct the amount, MyInvoiceOnline lets you raise a credit note against the original invoice. Reference the original, enter the adjustment (the returned items or the corrected figure) and the reason, then save the document and download or send it.

credit note preview

Box illustration

Create a VAT credit note online — enter the details and generate a compliant PDF.

Can I change an invoice after I’ve sent it?

Not by overwriting it. Raise a credit note that references the original to reduce or cancel it, or a debit note to increase it. Leave the original invoice in your records — HMRC expects a clear trail.

How long do I have to issue a VAT credit note?

If you're VAT-registered, HMRC's rule is within 14 days of the price change or refund, so your VAT return for that period reflects the adjustment. If you bill monthly, you can ask HMRC for an extension.

Does my credit note need to show VAT?

If the original invoice included VAT, yes — the credit note must credit the VAT in the same proportion as the original, or HMRC may treat it as invalid.

Do I need to send the credit note to my customer?

Yes. They need it to adjust their own records, and their input VAT if they're VAT-registered. Reference the original invoice number so both sides reconcile cleanly.

I only mistyped the address, not the amount. Do I still need a credit note?

If nothing about the value or VAT changes, you can usually re-issue a corrected invoice or send a short note. For small clerical errors that don't affect your customer's VAT, HMRC often lets you put things right on your next VAT return. A credit note is for changes to what's owed.

Can I amend an issued invoice on the Mini plan?

No. On Mini, an issued invoice is view-only. To edit invoices after issuing them, you'll need Premium (it also works during your free trial).

Use the template to quickly create an invoice
Invoices

Related articles

Invoice History: How to Track Whether Your Customer Received and Opened It
07/08/2026

You've sent an invoice but aren't sure whether your customer received and opened it? In MyInvoiceOnline, every invoice keeps a history of what happened to it. This guide shows where to find it and how to send invoices by email straight from the app.

Overdue Invoice: What to Do When a Client Hasn't Paid
05/08/2026

When an invoice is overdue, UK law is on your side: on business-to-business invoices you can claim statutory interest of 8% above the Bank of England base rate, plus fixed compensation of £40–£100 — automatically. Here's how to chase an overdue invoice, and how to track its status and send reminders inside MyInvoiceOnline.

How to create an invoice from an advance invoice
18/05/2026

Have you issued an advance invoice and your customer has paid the deposit? You can create the corresponding tax document in MyInvoiceOnline with a single click — the application will automatically pre-fill the line items, deduct the deposit, and link both documents together.

Downloading issued invoices in bulk
12/05/2026

Downloading invoices from MyInvoiceOnline.co.uk is quick and straightforward — whether you need documents for a specific period or by client. This guide walks you through both methods so you can pick the one that suits you best.