Invoice number

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Invoice number

You should definitely pay attention to this

The correct invoice number is more than just a number on the invoice. This is because the tax office insists that invoices are numbered correctly. If they are not, you can expect high additional charges. But even apart from that, you are well advised to use unique invoice numbers. After all, your customer will hold your invoice in his hands at some point.

What do I need to know?

A unique invoice number helps to assign a transaction exactly to an invoice. This is not only useful for you, but is also required by the tax office. In the event of a tax audit, you must be able to prove how many invoices you have written each year.

But that is not all. Each invoice number may only be assigned exactly once. In this way, you can ensure (in a way that is traceable for the tax office) that you have not billed products or services twice.

The regulations on how a legally compliant invoice number must be structured can be found, among other things, in the Value Added Tax Act Section 14 (4), which states what information an invoice must contain, namely “a sequential number with one or more series of numbers, which is assigned once by the invoice issuer to identify the invoice (invoice number)”.

Structure of an invoice number

As long as each number is assigned only once and the invoice can be clearly assigned to a specific transaction, the most important requirements are already met.

This also means that you are largely free to choose your own invoice numbers. Nowhere is it stipulated that the first invoice of the year must be 2020-001, for example.

The legal requirement merely states that it must be one or more number ranges that can be clearly assigned. How this or these number range(s) are structured is up to you.

Among others, the following invoice numbers are conceivable:

  • 31012020-001
  • 20203101-001
  • RE-NR-3101-2020-001
  • RE-NR-Jan31-2020-001
  • 123456789-KU-0815

You can almost let your imagination run wild if you like to create individual invoice numbers. However, this is not a default.

By the way, just as little as the assumption of some entrepreneurs that the invoice may only consist of numbers. As you can see in our examples, a combination of numbers and letters is also possible without further ado.

Rechnungsnummer Beispiel
Example invoice number

Gaplessness of numbers:
Yes or No?

Another common misconception is that invoice numbers must follow each other without gaps. But this is not the case. As long as you really only assign each invoice number once and this is also traceable, you do not have to ensure that there are no gaps.

This is because some business owners are concerned that if there were no gaps in the sequence, you would reveal too much about their company. Customers who receive invoice 2020-0001 one month and an invoice with invoice number 2020-0003 the next month can quickly calculate how many invoices were written last month.

Fortunately, however, you don’t have to transmit this information in your invoice number at all; you can opt for an individual sequence of invoice numbers.

vorsicht rechnungsnummer

Caution with manual assignment of the invoice number

As you can see, it is not that difficult to display the invoice with a correct invoice number. Nevertheless, you should not be careless. If you assign invoice numbers twice and the tax office notices this before you can correct the error, it can be expensive.

If the tax office notices irregularities and suspects double or even multiple entries under the same invoice number, there is a threat of a sales and profit estimate. And in most cases, this turns out to be unfavorable for the company.

Exception: small value invoices

For invoices under 250 euros (including sales tax or VAT), the tax office is somewhat more lenient. These invoices do not have to show a consecutive invoice number, but they may.


Avoid profit estimation:
use easybill

Want to save yourself the stress and worry of assigning a correct invoice number? Nothing could be easier!

  • Prepare legally compliant, unique invoice numbers
    no longer cause you grief

  • Each invoice is assigned a unique number that is assigned only one

  • Individualize your invoices according to your wishes: change the invoice number and create your own number ranges

Create invoices with easybill

Create legally compliant invoices very easy and fast with easybill.

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