Procedure
For taxpayers subject to church tax who are assessed for income tax, the church tax is determined together with the income tax by tax assessment notice.
For citizens subject to income tax, the church tax together with the income tax is withheld from the salary by the employer on the basis of the notified income tax deduction criteria.
The church tax of citizens who earn capital gains (e.g. interest on savings) and for whom income tax is deducted from the capital gains - the so-called Abgeltungssteuer - is levied, the church tax payable on it is levied as a surcharge on the Abgeltungssteuer since 01.01.2015.
The basis for this is the information provided to those obliged to deduct (usually the banks) that their customer belongs to a tax-raising religious community. The basis for the church tax deduction is given to the person obliged to deduct on the basis of an annual enquiry to the corresponding database. The database is maintained centrally at and by the Federal Central Tax Office.
For further details see. http://www.bzst.de/DE/Steuern_National/Kirchensteuer/kirchensteuer_node.html
The taxpayer can influence his church tax liability by joining or leaving the church. Both entering and leaving the church are done by a declaration to the respective church community. As a rule, the declaration must be submitted in person for recording. However, it can also be submitted to the church community in publicly or officially certified form. The registrar in whose district the declarant has his residence is responsible for the official certification.
The responsible parish reports on the entry or exit of the church to the respective registration office of the political municipality and thus also informs the responsible tax office accordingly.
In case of doubt, the taxpayer can also submit the corresponding report in person to the registration office responsible for him/her by presenting the certificate of entry or exit.