Quick steps
- Choose a format, such as INV-0001 or 2026-001, and stick with it.
- Start at 1 (or any number you like) and go up by one for each invoice.
- Never reuse a number, even if an invoice is cancelled.
- Keep quotes and receipts in their own sequences.
- Let the editor suggest the next number, or type your own.
Invoice numbering formats
| Format | Example | Good for |
|---|---|---|
| Simple sequence | INV-0001, INV-0002 | Most small businesses. Easy and clear. |
| Year + sequence | 2026-001, 2026-002 | Seeing at a glance which year an invoice belongs to. Restart the count each year. |
| Year + month | 2026-11-01 | Businesses that send many invoices a month. |
| Client code | ACME-001 | Tracking invoices per client. Keep an overall sequence too, so numbers stay unique. |
| Project code | WEB24-003 | Agencies billing several invoices per project. |
Invoiceferry starts invoices at INV-0001, quotes at QUO-0001 and receipts at RCT-0001, and suggests the next number each time. To start from a higher number, type it in the same format (for example INV-0101) and the editor continues from there. You can also type any other format, such as 2026-001, but then you enter each new number yourself.
Gaps, mistakes and cancelled invoices
- Don’t delete or reuse a number. In many countries, tax authorities expect an unbroken sequence and may ask about gaps.
- Made a mistake on a sent invoice? Issue a credit note to cancel it, then a new invoice with the next number. If the client hasn’t received it yet, you can usually correct it and keep the same number.
- Starting out? You don’t have to start at 1. Starting at, say, 0101 is fine, as long as the numbers go up from there.
- Switching tools? Continue from your last number, so the sequence carries on.
Frequently asked questions
Does an invoice number have to be sequential?
In many countries, such as the UK and most of the EU, VAT invoices must have a unique number from a sequence. Even where it is not required, sequential numbers make your records much easier to check.
Can I start my invoice numbers at 1000?
Yes. Any starting number is fine, as long as each new invoice is numbered higher than the last and no number is used twice.
Should quotes and invoices share numbers?
No. Give quotes their own sequence. When a quote is accepted, put the quote number in the invoice’s reference field so the two are linked.
What if I need to cancel an invoice?
Keep the number, mark it as cancelled in your records, and issue a credit note if it was already sent. The next invoice takes the next number.