I suggest
 
- to abolish completely the funding of all religious organisations and their activities from the state budget.
-to introduce an ADDITIONAL, let's call it a church tax, from which registered religious communities should be financed, with ONLY them being responsible for collecting this money.
- to introduce a system of voluntary payment EXCLUSIVELY by card, through which the collection of money by the religious communities could be controlled, and thus their taxation.
 
p.s. such examples already exist, for example in Sweden