> For the complete documentation index, see [llms.txt](https://wiki.dieagenturverwaltung.de/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.dieagenturverwaltung.de/die-agenturverwaltung-en/onboarding/nummernsysteme/gutschrifts-und-rechnungsnummern.md).

# Credit invoice and invoice numbers

### **Best practice for invoices**

The numbers consist of\
\<RG-prefix>-\<customer-code>-\<four-digit year>-\<three-digit sequential number>

> RG-TUI-2018-012\
> RG-BAB-2019-001

The three-digit sequential invoice number restarts at the turn of the year with 001. If there really are more than 999 invoices for a customer in one year, the number automatically becomes four digits.

#### Advantages of this pattern <a href="#vorteile-dieses-musters" id="vorteile-dieses-musters"></a>

* The number is suitable as a filename - even on a web server
* The prefix distinguishes between invoice and estimate
* In a file system, files named by invoice number automatically sort by customer, year and sequential number
* The customer code defines a separate number series for the customer

* Customers cannot deduce the agency's revenue
* If customer codes are established in the agency, they are easy to search by

#### Number ranges for **invoice numbers**

In addition, the agency software allows maintaining invoice numbers in so-called invoice number series.\
For example, you can open a separate invoice number series for each customer. **This way it is not apparent from the invoice number whether and how many invoices you issue to other customers**. German tax law permits maintaining such invoice number series.

Contact us if you have further questions on this topic.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://wiki.dieagenturverwaltung.de/die-agenturverwaltung-en/onboarding/nummernsysteme/gutschrifts-und-rechnungsnummern.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.