What to Consider with Invoice Numbers?

The Requirement

§ 14 Abs. 4 UStG requires a uniquely assigned, sequential number. Sequential does not mean continuously ascending by one – it means that the systematics are traceable and no number occurs more than once.

Multiple Number Ranges

Permissible, for example, by location, business area, or year. Important:

• No duplicate assignments within each range
• The systematics should be documented in the procedural documentation
• Gaps should be explainable

The Critical Moment: The Transition

If an old system continues to run in parallel during the transition, both systems can assign the same number. This is the most common mistake during implementation – and it often only becomes apparent months later.

Solution: Define separate number ranges before the transition, for example, with different prefixes.

What Causes Gaps

• Canceled invoices whose number is not reassigned – not critical, but document it
• Test invoices in the productive system – avoid
• Interrupted invoice creation that has already pulled a number

Practical Advice

The number should be assigned by the system, not manually. Manual assignment reliably leads to duplications as soon as more than one person writes invoices.

This text does not replace tax advice.