The office of the Expert Committee for Property Values receives copies of all property transactions in the city of Mainz (§195 BauGB). These purchase agreements are recorded on a property-specific basis and serve to create market transparency and enable the derivation of value-relevant data. The purchase price collection provides a good basis for comparison, particularly for undeveloped properties, standard houses (semi-detached, terraced, and end-of-terrace houses), and condominiums.

A small group of people who can guarantee the proper use of the information and compliance with data protection regulations (e.g., court experts, publicly appointed and sworn experts) can obtain the original data on request.

In individual cases, the data is available in anonymized form to all persons with a "legitimate interest."

The prerequisite for receiving information is an informal written request containing the following details:

• Background to the request
• Details of the property (street, house number or district, parcel, plot), living space, and year of construction
• Key date

usually 65 euros