Leaving a church, religious community or ideological community must be declared to the responsible office.

Do you want to leave a church?
Then you need to tell the right office.

This is how it works:

You are at least 14 years old.

Or:

You are not yet 14 years old.

But your parents are responsible for you.
Then your parents can declare your withdrawal from the church.

Are you 12 years old or older?

Then you can declare your withdrawal from the church yourself.
Your parents do not have to do this for you.
But you must say "yes" yourself.
You must make the declaration in person.

You are leaving the church.
The office (hard word: the authority) must know this.
You report this to the authorities.
The authority then sends a message to your boss.

You no longer have to go to the tax office.
You have to tell your boss:
You will no longer have to pay church taxes.