In some European countries, "church tax" is levied against members of certain religions. How each country handles this differs depending on each country's tax laws.
In Germany, a member of a religion that has "public law" status pays an additional 8 or 9 percent on their tax assessments. How this tax is collected is one of two ways: the government can collect the tax from each member and then disburse it to the religion they belong to or, the church/religion can collect the tax themselves directly from the membership.
In Germany, on the basis of tax regulations passed by the religious communities and within the limits set by state laws, communities may either require the taxation authorities of the state to collect the fees from the members on the basis of income tax assessment (then, the authorities withhold a collection fee), or choose to collect the church tax themselves.
In the first case, membership in the religious community is stored in a database at the Federal Tax Office which employers receive excerpts of for the purpose of withholding tax on paid income. If an employee's data indicate membership in a tax-collecting religious community, the employer must withhold church tax prepayments from their income in addition to other tax prepayments. In connection with the final annual income tax assessment, the state revenue authorities also finally assess the church tax owed. In the case of self-employed persons or of unemployed taxpayers, state revenue authorities collect prepayments on the church tax together with prepayments on the income tax.
If, however, religious communities choose to collect church tax themselves, they may demand that the tax authorities reveal taxation data of their members to calculate the contributions and prepayments owed. In particular, some smaller communities (e.g. the Jewish Community of Berlin) choose to collect taxes themselves to save collection fees the government would charge otherwise.
The church tax is only paid by members of the respective church. People who are not members of a church tax-collecting denomination do not have to pay it. Members of a religious community under public law may formally declare their wish to leave the community to state (not religious) authorities. The obligation to pay church taxes ends once such a declaration has been made. Some communities refuse to administer marriages and burials of (former) members who had declared to leave it.
So, based on the above information, once a person declares themselves a JW by signing that "consent form" (which is the concern of many right now because of the privacy laws coming into effect on data storing), their personal information about their job and finances that is submitted to the government, become accessible to the WT/Org (if the org chooses to collect the tax themselves). And, their affiliation with the JWs also is revealed to their employers.
Once a person is no longer a JW, and want to opt out of the church tax, they have to report that to state authorities, not to the religious authorities.
In Germany, the JWs have public law status which means that the above tax laws apply to them - the org can now collect taxes from their membership and they can access the tax records of all the JWs that have registered with them as members.
Predictably, this information has not been given to the JWs themselves and the org's write up about gaining public law status in Germany does not reveal how public law status gives the org the power to collect taxes and gain access to information about its members income. This is how the granting of public law status in Germany was written up for the org's website:
Oct 10, 2017
The Long Struggle to Obtain Public Law Status
The Benefits of Having Public Law Status
What are the real benefits of gaining public law status in Germany? The org can collect tax and not only that, they can access confidential income information on their members.
Does the org's article include that in the "benefits"? Of course not - 26 years of legal struggle is re-framed as a fight for religious freedom.
Just sign on the dotted line...give consent for the org to keep records on you and, in Germany, the org can access your income tax records.