Invoice Number Generator

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EU Invoice Number Requirements — Legal Guide

The EU VAT Directive (2006/112/EC) requires that every VAT invoice issued by an EU business carries a sequential invoice number. Article 226 of the Directive specifies that each invoice must contain a sequential number, based on one or more series, which uniquely identifies the invoice. This is a mandatory legal requirement — not optional formatting.

What Makes an Invoice Number Compliant?

Sequential: Numbers must follow a logical sequence with no gaps
Unique: Each invoice number must be used only once
Identifiable: The numbering must allow the invoice to be uniquely identified
Traceable: Tax authorities must be able to audit the full sequence

Accepted Invoice Number Formats in the EU

Format	Example	Best For
Year + Sequence	2026-001	Simple businesses, freelancers
Year + Month + Sequence	2026-03-001	High-volume monthly invoicing
Prefix + Year + Sequence	INV-2026-001	Multiple invoice series
Prefix + Year + Month + Sequence	INV-2026-03-001	Large businesses with departments
Prefix + Sequence	INV-001	Simple sequential only
Client + Year + Sequence	ACME-2026-001	Per-client invoice series

Invoice Number Requirements by Country

Belgium: Sequential numbering is mandatory. Each series must be clearly defined. The Belgian tax authority (SPF Finances / FOD Financiën) recommends including the year and a sequential counter. Credit notes must reference the original invoice number.

Germany: The Umsatzsteuergesetz (UStG) §14 requires a consecutive invoice number. Gaps in sequences are technically not permitted and can trigger tax audits. Many German businesses use YEAR-SEQUENCE format (e.g., 2026-0001).

France: The CGI (Code Général des Impôts) requires sequential numbering without interruption. French invoices typically use a format combining year, month and sequence: 2026-03-001.

Frequently Asked Questions

Can I have gaps in my invoice number sequence?

Technically no — EU VAT law requires sequential numbering without gaps. In practice, if an invoice is cancelled, it should be voided (kept on record) rather than deleted, and the next invoice should use the next sequential number. Tax authorities may question large unexplained gaps in sequences.

Can I use multiple invoice number series?

Yes. The EU VAT Directive allows one or more series of invoice numbers. You can have separate series for different clients, departments, or document types (e.g., INV-2026-001 for invoices, CN-2026-001 for credit notes). Each series must be sequential within itself.

Should I restart invoice numbering each year?

This is optional. You can either continue sequentially across years (INV-0001, INV-0002...) or restart each year (INV-2026-001, INV-2027-001). Including the year in the format is recommended as it makes archiving and retrieval much easier, especially for multi-year VAT audits.

Is the counter really saved between browser sessions?

Yes. The counter is saved in your browser's localStorage, which persists between sessions on the same device and browser. It is not stored on our servers. If you clear your browser data or use a different device, the counter will reset. For production use, we recommend tracking invoice numbers in your accounting software.