Sounded like BS to me, but it turns out to be true [en.wikipedia.org] and also several other countries are using taxes to support religious institutions.
What a great scam! We need to figure out how to get a piece of that for some atheist communities.
It is just leveraging the state tax collection machinery on behalf of churches but it's voluntary. You don't have to "officially register" as a member of those groups if you don't want to.