Guide Tenancy law
Rent increases: the routes, the reasons, the periods
A rent increase only works if the route chosen, the reasons given and the periods fit together. Which routes are open is often decided by the lease itself.
Four routes to a higher rent
The law knows four routes: an increase up to the local comparative rent (§ 558 BGB), an increase after modernisation (§ 559 BGB), graduated rent (Staffelmiete, § 557a BGB) and index rent (Indexmiete, § 557b BGB). Graduated and index rent must be agreed in the lease. While graduated or index rent applies, an increase to the comparative rent is excluded.
Up to the local comparative rent
The landlord may ask the tenant to agree to a higher rent if the rent has been unchanged for fifteen months; the request itself may be made one year after the last increase at the earliest (§ 558 (1) BGB). Within three years the rent may rise by no more than 20 per cent, and by no more than 15 per cent in municipalities the federal state has designated as having a strained housing market (the cap, § 558 (3) BGB). Whether the lower cap applies to your flat, I check against the current Hessian regulation.
The request must be in text form and give reasons, usually the rent index (Mietspiegel), otherwise an expert opinion or three comparable flats (§ 558a BGB). Where there is a qualified rent index, as in Frankfurt am Main, the letter must state its values even if it relies on something else.
The tenant has until the end of the second calendar month after receipt to agree. If the tenant agrees, the new rent applies from the third calendar month after receipt. If not, the landlord may sue for consent within three further months (§ 558b BGB).
After modernisation
After modernisation the landlord may raise the annual rent by 8 per cent of the costs spent on the flat (§ 559 BGB). Costs that fall on maintenance due anyway are deducted. Within six years the rent may rise by no more than 3 euros per square metre this way, or 2 euros where the rent is below 7 euros per square metre. The modernisation must be announced in text form at least three months before it starts (§ 555c BGB); without that announcement the start of the increase may be delayed by six months (§ 559b BGB).
Graduated rent and index rent
With graduated rent, the lease already says when the rent rises and by how much. Each step must last at least one year and be stated as an amount in euros (§ 557a BGB). With index rent, the rent follows the consumer price index of the Federal Statistical Office. It may be adjusted at most once a year, by a declaration in text form that states the change in the index and the new rent; the new rent applies from the month after next (§ 557b BGB).
When a flat is let anew, the rent brake (Mietpreisbremse) may also limit the permitted rent: for graduated rent each step, for index rent the starting rent. Whether it applies to a flat depends on the state regulation and on exceptions, for example for new buildings.
How I help
I check which route is open and how far it goes, calculate the increase, draft the request with the right reasons, and represent you if the tenant does not agree. If you are a tenant who has received a request, I check it before the period for agreeing runs out.
This guide gives a general overview and does not replace advice on your own case. As of 1 October 2026.
Frequently asked questions
May I raise the rent by email?
Yes. A request for the comparative rent only needs text form, so an email is enough if it identifies the landlord. In a dispute, though, the landlord must prove that it arrived; a letter with proof of delivery is therefore often the safer route.
What happens if the tenant does not agree?
The landlord may then sue for consent within three months after the period for agreeing ends. If that deadline is missed, a new request is needed.
How often may I raise the rent?
An increase to the comparative rent may be requested one year after the last one at the earliest and takes effect fifteen months after it at the earliest; within three years the cap applies as well. Increases after modernisation or for higher operating costs do not count towards either.
Do I have to announce a modernisation in advance?
Yes, at least three months before the work starts, in text form, with the kind and extent of the work, when it starts and how long it lasts, and the expected rent increase (§ 555c BGB). The announcement should also tell the tenant that financial hardship may be claimed.
Your matter
Describe your matter briefly by email, call, or book an appointment directly. You will receive a reply within two days.