Assigning invoice numbers correctly
The invoice number is a mandatory detail. It lets the tax office assign every invoice unambiguously.
What the law requires
Under section 14 (4) UStG every invoice must carry a consecutive number that is unique. It may consist of one or more series of numbers or letters. The law does not require a specific form, and a missing number is not automatically a mistake.
Examples of sensible numbers
- 2026-0042: year and running number
- INV-2026-0042: with a prefix for the document type
- 2026-10-0042: year, month and running number
- K12-2026-0007: customer number as part, if you count per customer
Several number ranges
You may count separately, for example for invoices, credit notes and quotes, or for several locations or companies. Each range must be consecutive and unambiguous in itself, and you should be able to explain how the ranges are built.
Gaps and cancellations
Gaps stand out in an audit. You should be able to explain them, for example with a cancelled invoice. If you withdraw an invoice you do not delete it but cancel it with a cancellation invoice. The number of the cancellation invoice continues in the range of credit notes or invoices.
When you switch from other software
When you switch you continue the count. Set the next number in the new software so that it is higher than your last previous invoice so that no number appears twice.
How Saldiqo helps
Saldiqo assigns the number only when you finalize, consecutively per document type and year, and locks it against changes afterwards. You set the format yourself and when you move you carry over your existing count.
Frequently asked questions
May there be gaps in invoice numbers?
The law requires a consecutive, unique number. Gaps are not forbidden but should be explainable.
May I put the year in the number?
Yes, that is common and helps with assignment.
What about drafts?
A draft is not an invoice yet. The number is only created when you finalize.
Can I start at zero?
Yes, for a new company. When you switch you continue your existing count.
How do I cancel an invoice?
With a cancellation invoice that refers to the original number.
Try Saldiqo for free
Write invoices, create e-invoices, match payments and send reminders: free and without a trial period.
Start for freeMore guides
- E-invoicing in Germany: obligation, formats and deadlines
- The EÜR (cash-basis profit calculation) explained simply
- GoBD for self-employed people: the essentials
- Invoicing as a small business: how to do it right
- Writing a payment reminder: deadlines, interest and fees
- Writing an invoice: the mandatory details under section 14 UStG
- XRechnung or ZUGFeRD: what is the difference?
As of October 2026. General information, not legal or tax advice, without guarantee. For questions about your case ask your tax adviser.