How to create reference numbers for letters

How do I create a meaningful invoice number?

The most sensible invoice number is a sequential numerical invoice number in order to keep track of the invoices in the outgoing ledger. You can find out in the article what the purpose of the outgoing invoice book is and why excessive creativity with invoice numbers can be detrimental.


Legal regulation of invoice numbers

Often times you will find the answer in the law. Here: Sales Tax Act, namely Paragraph 14, the "Standard for issuing invoices".

The fourth paragraph regulates what needs to be on an invoice. We explained this in the article on mandatory information on an invoice.

Sentence four defines the same invoice number: "(...) a consecutive number with one or more series of numbers that is issued once by the invoice issuer to identify the invoice (invoice number) (...)".

Let’s unravel this text.

Invoice number: simple and unique

Basically: creativity is beautiful, but should not necessarily be lived out with the invoice number. Especially when you write a lot of invoices, you can quickly get confused.

The simplest system is: start at 1 and number consecutively. And because the Debitoor invoicing program doesn't like to make things unnecessarily complicated, this is exactly the system that is used for your invoice numbers.

Another great advantage of an invoice program is that each invoice number is guaranteed to be issued only once - errors are excluded.

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The simpler the invoice number, the better

It is best if you do not bother with the invoice numbers and you can easily keep track of them.

Tip: Keep your invoice number simple!

Start with number one. If you have two number ranges at your disposal, you could choose an even number series, i.e. 2,4,6, ... and an odd number, i.e. 1,3,5, ...

Skip invoice number?

The good advice is 'no'. The number should be consecutive. Accordingly, you should avoid gaps and large jumps in the invoice number as much as possible. Otherwise, you have to prove that you have not "deleted" any invoice and that you can use your bank account to show all transactions without any gaps. If an incoming payment is not covered by an invoice, you can be accused of tax evasion.

This has in practice two advantages:

1. It's easy for the tax office and doesn't have to ask unnecessary questions
2. You do not have to explain yourself to the tax office.

Who wants to discuss with the tax office?

Unique thing for the invoice numbers

Each invoice may only be issued once. Since the invoice number, as just learned, has to be on the invoice according to the sales tax law, it can consequently only be unique.

The principle of uniqueness has top priority in jurisprudence.

And let's be honest, who doesn't want to be unique?

The thing with the outgoing invoice book

A long word: Invoice Output Book; is regulated in Section 238 of the Commercial Code.

Sorry, another legal passage.

But so is “(...) Every merchant (...) is obliged to keep books and to make his commercial transactions and the position of his assets evident in these according to the principles of proper bookkeeping. (...) "

In short: You should list all of your invoices and back them up with originals.

Important: The archiving principles stipulate the obligation to retain invoices for a period of 10 years. Archiving in an accounting program such as Debitoor does not release you from the retention obligation.

Outgoing invoice book and invoice number?

In the outgoing invoice book, it is helpful, practical and clear if you only use one consecutive invoice number.

You, your accountant and the tax officer don't get mixed up. Good vibrations are always good. In addition, §238 HBG even defines that a third party must be able to quickly look through your documents.

If the check takes an eternity, i.e. an almost unreasonable time, the tax office will recommend that you start over and ask unpleasant questions. You weren't trying to cheat something, did you? Unfortunately, a "no" answer is not enough.

Rule of thumb: Look at your accounting through the eyes of a tax official.

What is a useful invoice number now?

Back to top. The little digression will surely help you to answer the initial question better.

A meaningful invoice number is easy. There is no place for excessive creativity.

Still, in the end you have to decide for yourself what makes sense.

For example, if you only have 5 customers and your program provides several number ranges, you could also use letters as a prefix.

Example of creative invoice numbers

For customer “apple” you could write: AP-1 date. And for the customer “window”: FE-1 date.

Main thing: Don't get confused.

In some invoice programs you have the freedom to determine the invoice number yourself. Just make the best of it.

Already knew?
In the Debitoor invoice program, you enter an invoice number at the beginning and the system continues to count from then on. Very easily.

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