In countries that collect church taxes on behalf of the church, it can be necessary to officially de-register your religion to avoid paying taxes to the church.
A lot of churches/temples are membership-based. You can probably still attend sermons and the like in most cases if you’re not a member, but they won’t let you have a wedding, baptize your baby etc. in their temple.
I don’t ever see it being helpful in life to register your religion.
In countries that collect church taxes on behalf of the church, it can be necessary to officially de-register your religion to avoid paying taxes to the church.
https://www.pewresearch.org/short-reads/2014/09/22/in-some-european-countries-church-membership-means-paying-more-taxes/
It’s mostly in death so people put you in the right cemetery.
I would worry more about being rounded up depending on your id and who’s in charge than being put in the right place.
A lot of churches/temples are membership-based. You can probably still attend sermons and the like in most cases if you’re not a member, but they won’t let you have a wedding, baptize your baby etc. in their temple.