Qualified rent index: why its figures carry weight in court

Simple index or qualified index

German law has two tiers. A rent index (Mietspiegel) under Section 558c BGB is any overview of local reference rents drawn up or approved by the competent municipal authority, or jointly by landlord and tenant associations. The provision does not say how the figures must be produced. A simple index (einfacher Mietspiegel) may rest on a survey, on what agents and associations observe, or on a negotiation between the tenants’ association (Mieterverein) and the owners’ association. It should be brought into line with the market every two years. Municipalities with more than 50,000 inhabitants have to produce one, and every index must be published.

The higher tier is set out in Section 558d BGB. An index is qualified when it is drawn up on recognised scientific principles and approved. In practice that means a representative sample of rents agreed or changed in the previous six years, a documented statistical analysis (a table or a regression model) and a report explaining each step. Proof is made easier in two ways. An index that meets the requirements of the federal regulation issued under Section 558c(5) BGB is presumed to be scientific. So is an index that both the authority and the associations on both sides have recognised as qualified.

What the presumption does in a dispute

The key rule is Section 558d(3) BGB: as long as the update deadline is met, the rents shown in a qualified index are presumed to reflect the local reference rent. For a rent increase under Section 558 BGB this means that if the landlord asks for a rent inside the range the index gives for your flat, you need solid grounds to refuse consent. If he asks for more, the burden is on him. Many cases can then be decided without an expert valuation, which is slow and expensive.

A simple index lacks the presumption. It remains a permitted way of justifying an increase under Section 558a(2) BGB, and courts often use it when nothing better is available. But if one side disputes its figures with real arguments, an expert report frequently settles the matter. The same is true for the reference rent under the rent brake (Mietpreisbremse): a qualified index gives you a figure you can rely on, a simple one only an indication.

Which large cities have a qualified index

Of the 14 cities whose indexes this site covers, 12 are qualified. Cologne and Düsseldorf use simple indexes published by associations. In Cologne a working group draws up the index and the Rhineland property exchange publishes it; in Düsseldorf the owners’ association Haus und Grund and the tenants’ association agree it between them. Both are useful, but neither carries the presumption of Section 558d(3) BGB.

Several qualified indexes are updates rather than new surveys. Bremen and Essen have carried the figures of their last survey forward with the consumer price index, and Dortmund and Nuremberg have also updated theirs. The law allows this: Section 558d(2) sentence 2 BGB accepts either a sample or the movement of the price index for all private households as the basis for an update. The presumption survives, but the deadline for a fresh survey keeps approaching.

The deadlines: update after two years, rebuild after four

A qualified index must be adjusted to the market every two years and produced afresh after four. Since the reform of rent index law, Section 558d(2) sentence 4 BGB measures these intervals by the reference date on which the data were collected (Stichtag), not by the date of publication or of the council decision. The reference date of the updated version may therefore be at most two years after that of the previous one, and the reference date of a new edition at most four years after the last survey. Sentence 5 applies the same rule to publication. Because a year often passes between the survey and the index taking effect, many indexes stay in force well beyond what the two-year rule seems to suggest.

The table uses only reference dates that the cities give as a calendar date and adds two and four years. It shows the latest data date the next version must refer to, not the day it has to appear. For Leipzig and Dresden that point has already passed; whether the next edition meets it will only show from its own reference date. Next in line are and , on 1 April 2027. The small calculator above works out the same dates for your own city once you enter the month and year of the reference date given in the index or its method report.

What if a city misses the deadline? The index loses its presumption but does not become void. Section 558a(4) BGB expressly lets a landlord base an increase on an outdated index, or on the index of a comparable town, when no index meeting the deadlines exists. In a dispute those figures weigh less, and either side can ask for an expert valuation.

What the landlord must quote from a qualified index

The rule with the most practical bite is Section 558a(3) BGB. If an up-to-date qualified index has figures for your flat, the landlord must state them in his increase letter even when he justifies the increase by something else: three comparable flats, a rent database (Mietdatenbank) or an expert report. He cannot sidestep the presumption by keeping quiet about it. In every letter, check:

• Does it name the field or calculation from the index, with the range and the mean or the computed value?
• Are the features the landlord used correct: year of construction, floor area, location, fittings?
• Is the demanded rent inside the range? Under Section 558a(4) sentence 1 BGB that is enough to justify the letter; whether the rent is also right on the merits is a second question.
• Is the increase cap respected? The index says nothing about how far your rent may rise within three years.

Berlin and Hamburg allow their tables to be reproduced, so the calculator shows the matching value with its row and field there (Berlin rent index 2026, Hamburg rent index 2025). For other cities it links to the city’s own online calculator, because their reservation of rights rules out copying the figures. The rent index page explains where to find each one.

A three-step check

1. Find out whether your index is qualified and which reference date it states.
2. Count two and four years from that date; if your increase letter is dated later and there has been no update, the index no longer carries the presumption.
3. Compare the demanded rent with the value for your flat and let the rent increase calculator check the cap and the deadlines.