A rent index gives you an overview of the rents of comparable apartments in the city or municipality. It contains indications that:

• whether a request for a rent increase by the landlord is justified,
• whether the rent is permissible in the case of re-letting if the apartment is located in an area in which the provisions of the so-called rent brake apply,
• whether the rent is reasonable in principle (outside the scope of the so-called rent brake).

On the basis of net rents that have been newly agreed or changed in the last six years, the rent index shows the average rent net cold (local comparative rent) in euros per square metre per month. This comparative rent can be higher or lower for each individual apartment. The criteria for this are listed in the rent index.

For example, the following can be decisive:

• Apartment size
• Age of construction
• Area
• energetic state of modernization and
• Equipment of the apartment, for example, central heating, indoor toilet, parquet floor.

The local comparative rent may differ from the current market rent.

Rent indexes are drawn up jointly by representatives of landlord and tenant interests, such as tenants' associations, homeowners' and landowners' associations, or by the cities/municipalities. A city/municipality should draw up a rent index if there is a need for it.

For municipalities with more than 50,000 inhabitants, according to the Act on the Reform of the Rent Index Act, there will be an obligation to compile simple rent indexes in the future (entry into force on 1 July 2022).

As a rule, rent indexes should be adjusted and published every two years in line with market developments.

Rent indexes exist in many larger cities and municipalities.