Invoice number: Definition, legal requirements and design tips
The invoice number is a unique identifier that identifies each invoice and is essential for the organization and for tax evidence. Their uniqueness and sequential numbering ensure the clear allocation of invoices and protect against possible inquiries or sanctions from the tax office.
Why is the invoice number so important?
The invoice number is primarily used for traceability and regularity of your invoices — especially for the tax office. Since every invoice contains a sales tax that has to be paid to the tax office, the unique and consecutive numbering is an important indicator that all transactions have been correctly recorded in the accounting department. For business customers, the invoice number is also proof of input tax deduction.
What are the legal requirements?
💡 §14 paragraph 4 no. 4 Sales Tax Act 💡
Each invoice must contain a sequential number, which is assigned once for unique identification.
That means:
- Complete order is not mandatory: Numbers must be consecutive, but occasional gaps may be explained comprehensibly.
- Alphanumeric numbers are allowed: Letters can also be used, for example to additionally identify regions, departments or years.
- Number ranges possible: You may use multiple number ranges (e.g. by year or geographical area) as long as each invoice number remains unique.
Make the invoice number simple and clear
A simple and frequently used method is sequential numbering, starting with a number of your choice. For example, your first invoices could be numbered 1001, 1002, 1003, and so on. It is important that every number is unique.
Include time components in the invoice number
An year code, such as 2024001 for the first invoice in 2024, can be useful to make the numbering even clearer. This type of identification helps to assign invoices to specific periods of time right away.
Insert organizational components
If you want the invoice number to include even more specific information, you can include a combination of departments, teams, or geographical areas, for example. For example, an invoice number such as BER-2024-0001 indicates that the invoice was issued in Berlin and generated in 2024. This gives you an easy way to allocate invoices.
Assigned to an invoice number multiple times?
If you assign an invoice number twice, the tax office can carry out a verification as it may assume multiple transactions. In the worst case, there may be additional tax claims or even criminal consequences. Discover the bug in the Invoicing In good time, inform your customers and create a cancellation invoice and a new invoice with a correct invoice number.
Conclusion
The invoice number is an indispensable element of every invoice and plays a central role in proper accounting and tax processing. Their continuous and one-off allocation protects against potential tax disadvantages and enables clear traceability of sales flows. Entrepreneurs should comply with legal requirements and ensure that each invoice number is unique in order to meet the requirements of the tax office.
By strategically designing the invoice number, additional information can be integrated to make it easier to organize and identify invoices. Careful handling of the invoice number is crucial to avoid legal problems and increase accounting efficiency.