Everything you need to know about adjusting rent according to the index (Indexmiete Anpassung)

What is an Indexmiete (indexed rent)?

An Indexmiete (indexed rent agreement) is a rental contract in which it is agreed that the rent may be adjusted up or down according to the development of the consumer price index (Verbraucherpreisindex).
This index is published by the Federal Statistical Office (Statistisches Bundesamt).
The purpose of this type of contract is to preserve the real value of the rent over time and to keep it in line with inflation.

When can the rent be adjusted?

• The rent may only be adjusted after at least 12 months have passed since the last adjustment.

• The landlord must inform the tenant in writing, stating

  • the percentage of change, and

  • the underlying index figures (previous and current consumer price index).

How is the adjustment calculated?

• The consumer price index at the beginning of the contract or at the last adjustment is compared with the current index level.

• The percentage change is calculated from this difference.

• This percentage is then directly applied to the current net rent.

• No additional rent increases are allowed at the same time (for example

  • increases based on the Mietspiegel (local rent reference), or

  • increases due to improvements or modernisation).

Illustrative example

• Basic rent (net cold rent): €800

• If the index rises by 5%,

  • the landlord may adjust the rent to €840.

What are the tenant’s rights?

• Transparency:
  The tenant must receive a written notice that clearly explains

  • which index level was used before,

  • the current index level, and

  • how exactly the new rent has been calculated.

• No combination with other rent increases:
  With an index-linked rent agreement, the landlord cannot additionally raise the rent based on

  • the Mietspiegel, or

  • improvements and modernisation,
    as long as the rent is governed by the index clause.

• Right to verification:
  The tenant may check the figures and, if in doubt,

  • ask for further clarification in writing, or

  • consult a tenants’ association (Mieterverein) or a legal adviser.

Can the rent be reduced?

Yes.
If the consumer price index goes down, the tenant in principle has the right to demand a reduction of the rent.
In practice, this situation is rather rare, as inflation usually causes the index to rise over time.

Relationship to additional costs (Nebenkosten)

• Nebenkosten (service charges, operating costs) are not affected by the index adjustment.

• They continue to be settled separately, either

  • according to actual consumption, or

  • based on the agreed advance payments and distribution keys.

• The index adjustment applies only to the basic net rent, not to the additional costs.

What happens if the tenant refuses the adjustment?

• If the landlord’s notice is formally correct and served in writing, the adjusted rent becomes due as of the month following the notice.

• If the tenant disagrees, the landlord may enforce the adjusted amount through legal proceedings.

• A mere dispute over the amount of the index-linked adjustment does not automatically justify immediate termination of the tenancy; any conflict must be clarified by a court.

Practical tips

• Keep copies of all adjustment notices and your rental contract.

• Check the official consumer price index yourself whenever you receive such a notice.

• In case of doubt or disagreement, seek advice from a tenants’ association or a lawyer specialised in tenancy law.

Conclusion

Adjusting the rent according to the index (Indexmiete Anpassung) is a flexible legal instrument designed to balance the interests of landlords and tenants by linking the rent to market conditions and inflation.
Understanding how this mechanism works helps you avoid conflicts, assess increases more accurately and ensure financial transparency in your rental relationship.

The editorial and author team of the website strives to provide accurate information based on careful research and multiple sources. Nevertheless, errors may occur or some information may not yet be fully confirmed. Therefore, the information contained in these articles should be regarded as an initial point of reference, and you should always contact the competent authorities and bodies for binding and confirmed information.