Invoice numbering

Dutch law requires a unique, sequential invoice number. EenFactuurMaken.nl takes care of it. You set the format under Settings → Invoices & numbering.

How it works

• An invoice only gets a number when you finalise it. A draft has no number, so deleting a draft never leaves a gap.
• Invoices and credit notes each have their own sequence.
• Finalising two invoices at the same moment (through the API, for example) can never produce the same number.
• A cancelled invoice keeps its number, so your sequence stays complete.

The format

The default is {YYYY}-{SEQ:4} for invoices (2026-0001, 2026-0002, …) and C{YYYY}-{SEQ:4} for credit notes (C2026-0001).

Tokens

Format rules:

• It must contain {SEQ} or {SEQ:n} exactly once.
• Otherwise you can use letters, digits and the characters - _ / . #. At most 50 characters.
• Year and month come from the invoice date, not from today.

Examples: F{YY}{SEQ:3} becomes F26001, {YYYY}/{MM}/{SEQ:3} becomes 2026/03/001, INV-{SEQ:5} becomes INV-00001.

Restart every year

With Restart at 1 every year (on by default) the sequence number restarts at 1 every year. Your format must then contain {YYYY} or {YY}, otherwise you'd get the same numbers every year.

If you turn it off, the sequence number simply continues across years.

Next number

The settings page shows under Next numbers which numbers your next invoices will get. Moving from another program? Set the Next sequence number to the number after your last invoice, so your sequence continues. If you lower it, we warn you: that can cause duplicate numbers or gaps. EenFactuurMaken.nl always refuses a number that already exists.

Choosing your own number

When you finalise, you can replace the proposed number with your own. It must be unique within your account. If it already exists, you'll see This invoice number is already in use. If it doesn't come after your last used number, you get a warning, because your numbers should go up.

Invoices dated in the past

Finalising an invoice dated in December while it's already January? It gets the next number from that previous year's sequence, for example 2025-0042. That keeps both years sequential.

Can I use several sequences?

Yes, the tax authority allows that, as long as each sequence is continuous. EenFactuurMaken.nl has one sequence for invoices and one for credit notes.