Concerning Switzerland (other countries are probably similar, e.g. Germany) (from https://awa.zh.ch/internet/volkswirtschaftsdirektion/awa/en/... ):
When registering in the municipality of residence, you will be asked about your religious denomination. In the Canton of Zurich, members of the Evangelical-Reformed (Protestant), the Roman-Catholic and the Christian-Catholic Church are required to pay church taxes. Church tax is levied along with the income tax and tax on assets. It amounts to between 8 and 16 percent of the cantonal base tax (“einfache Staatsteuer”) for members of the Catholic Church, between 7 and 15 percent for members of the Evangelical-Reformed (Protestant) Church and 14 percent for members of the Christian-Catholic Church.
As I already pay that, and as it's not a small amount, I was hoping that at least what I donate directly whenever I'm in the Church (the small box into which people put their donations - don't know how it's called), was used exclusively for the poor and not for something else?