There are quite a few customs authorisations. Here is an overview. And you can read how to apply for and change authorisations.
Overview of customs authorisations
Check out which authorisations are available. Most of the application forms and explanatory notes can be directly downloaded.
How do I apply for a customs authorisation?
Read how to apply for an authorisation. And how long it takes to get one.
How can I change or add something to my customs authorisation?
Do you need to change something in your customs authorisation? You fill in the application form for the permit again.