Invoice Numbering: Best Practices and Common Mistakes
Sequential, unique, no gaps — sounds simple, but invoice numbering trips up more sellers than you'd think. Here's how to get it right.
Invoice numbering seems trivial until you get it wrong. The Dutch tax authority requires sequential numbering — and "sequential" has a very specific meaning.
The rules
- Each invoice number must be unique — No duplicates, ever
- Numbers must be sequential — They should follow a logical order (1, 2, 3 or 2026-001, 2026-002, etc.)
- No gaps — If INV-005 exists, INV-004 must also exist (even if voided)
Common numbering formats
There's no required format, but these work well:
- YEAR-NUMBER — e.g., 2026-0001 (resets each year)
- PREFIX-NUMBER — e.g., MI-0001 (company prefix + sequential)
- Simple counter — e.g., 1, 2, 3 (works but less informative)
Mistakes to avoid
Using order numbers as invoice numbers. Order numbers come from the marketplace and may have gaps, duplicates across platforms, or non-sequential patterns. Always generate your own invoice numbers.
Resetting mid-year. If you switch invoicing tools in June, don't restart at 001. Continue the sequence from where the previous tool left off.
Multiple sequences. Running separate numbering for Bol.com and Shopify creates complexity. Use one sequence across all channels.
How automatic invoicing handles this
With automatic invoicing, numbering is handled for you. Each invoice gets the next number in the sequence, with your preferred prefix and format. No gaps, no duplicates, no manual tracking.
