Invoice numbers and fixing mistakes
Why invoice numbers run in order, how annual resets work, and the right way to correct an invoice without leaving a gap.
Invoice numbers are boring until an audit, a dispute or a payment sent twice. A simple, steady sequence protects you in all three.
What a good number looks like
CRA doesn't set a format, but each invoice must be easy to identify and your records must be complete. Numbers in order are the simplest way to show nothing is missing.
- Unique across your whole history, not just this year.
- Given out in order, with no gaps you can't explain.
- Never reused, even when an invoice is cancelled.
- Separate sequences for invoices, estimates, credit notes and receipts.
A common pattern is a prefix, the year and a counter, like INV-2026-0001. The year makes it safe to restart the counter each January.
Fixing a mistake
Don't delete a sent invoice. Issue a credit note that points to it, then send a new invoice with the right details. Both stay in your records, and the link between them explains the change. See Credit notes and refunds.
How CollabNorth numbers
- The number is assigned when you send, so drafts don't use up numbers.
- Two people sending at the same moment can never get the same number.
- Invoices, estimates, credit notes and receipts each have their own sequence, with an optional yearly reset.
- Once sent, the number and amounts are locked.
This is general information to help you keep your own records. It is not tax or legal advice.
Based on: CRA: Business records
Last checked: 2026-10-12