---
title: "Invoice numbering · EenFactuurMaken.nl"
description: "How EenFactuurMaken.nl keeps your invoice numbers sequential and gap-free, how to set the format with {YYYY}, {SEQ:4} and other tokens, and how to choose your own number."
url: "https://eenfactuurmaken.nl/en/docs/invoices/numbering"
markdown_url: "https://eenfactuurmaken.nl/en/docs/invoices/numbering.md"
language: "en-GB"
---

# Invoice numbering

How EenFactuurMaken.nl keeps your invoice numbers sequential and gap-free, how to set the format with {YYYY}, {SEQ:4} and other tokens, and how to choose your own number.

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

| Token | Becomes | Example |
| --- | --- | --- |
| `{YYYY}` | Year, 4 digits | 2026 |
| `{YY}` | Year, 2 digits | 26 |
| `{MM}` | Month, 2 digits | 03 |
| `{SEQ}` | Sequence number without leading zeros | 7 |
| `{SEQ:n}` | Sequence number with n digits (n up to 10) | `{SEQ:4}` becomes 0007 |

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.

Last updated on 13 October 2026