Guide · 8 min read

Rent increase 2026 — how often and by how much?

You want to increase the rent because costs are rising — but the BGB protects existing tenancies. We show the 3 permissible routes (comparative rent, index-linked rent, modernisation), the deadlines, capping limits and the legally compliant wording of the increase letter.

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Three ways to increase the rent

1. Rent increase to the locally customary comparative rent (German Civil Code) — the standard route
2. Index-linked or graduated rent — only if agreed in the contract
3. Modernisierungs-Umlage (Common law) — nach Sanierungen

Route 1: reference rent (German Civil Code) — step by step

Requirements:

The tenancy agreement has run unchanged for AT LEAST 15 months
The last increase must have been AT LEAST 15 months ago
The requested rent is BELOW the locally customary comparative rent (Mietspiegel!)
The increase does not exceed the capping limit (15-20 % over 3 years)

Written justification required:

Reference to the Mietspiegel (standard) — attach an extract of the relevant Mietspiegel fields
Three comparable flats (same location/size/fittings) — state address + rent
Expert appraisal — for special flats
Rent-database information (available only in Berlin)

Deadline + process:

The tenant has 2 months to CONSENT (period for consideration + period for consent, §558b BGB)
Effective from the 3rd month after receipt of the letter
If the tenant does NOT consent: the landlord can SUE for consent (§558b para. 2 BGB)
The claim must be filed within 3 months of the expiry of the consent period

Your utility bill statement in 10 minutes instead of 3 hours

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Capping limits 2026

Standard: 20 % in 3 Jahren (§558 Abs. 3 S. 1 BGB)
In rent-cap (Mietpreisbremse) areas: 15% over 3 years (§558(3) sentences 2-3 BGB)
Examples of 15 % areas: Berlin, Munich, London, Cologne, Manchester — all ~410 designated cities

Route 2: index rent

The tenancy contract can contain an index clause (§557b BGB): the rent rises automatically in step with the consumer price index (CPI) of the Federal Statistical Office. Advantages:

No application, no tenant consent required — the increase takes effect automatically
Rent increase linked to inflation — approx. +2.5 % permissible in 2025
The rent cap (Mietpreisbremse) and the capping limit do NOT apply

Disadvantages:

In a deflationary phase: the rent can theoretically fall
A modernisation surcharge in parallel is excluded (index increase only)
Klausel muss EXAKT formuliert sein — sonst unwirksam

Route 3: modernisation (German Civil Code)

After modernisation measures (thermal insulation, new heating, new windows, new lift, energy-efficient refurbishment), the annual rent may be increased by at most 8 % der investierten Modernisierungs-Kosten be increased.

Cap since 2019: Increase of max. €3/m²/month (for existing rents <€7/m²: max. €2/m²/month) within 6 years (§559(3a) BGB). This hardship clause protects tenants against rent jumps >50%.

Requirements:

Modernisation announcement in text form 3 months before commencement
Itemised breakdown of the anticipated costs + rent increase
The tenant has a special right of termination as of the start of the measure
Erhaltungs-Aufwand (Reparatur, Instandhaltung) IST ABZUZIEHEN — nur echte Modernisierungs-Wertsteigerung umlegbar

Sample rent-increase letter (Route 1: reference rent)

Subject: Rent increase under German Civil Code for the flat at [address] Dear Ms/Mr [surname], With this letter I request your consent to a rent increase of the current net cold rent from [XXX,XX] € to [YYY,YY] € (an increase of [Z,Z]%). The new rent takes effect from [date + 3 months after receipt of this letter, on the first of the month]. Grounds: The rent requested lies within the local reference rent of the Mietspiegel (rent index) for [city] in its respective current version. For a flat of [m²], year of construction [YYYY], fittings [standard/comfort/etc.] and location [simple/medium/good] the relevant figure is: — Mietspiegel average: [X,XX] €/m² — Upper range value: [Y,YY] €/m² — Rent requested per m²: [Z,ZZ] €/m² The demand therefore lies within the permitted range. The rent increase amounts to [P]% and thus corresponds to the capping limit under §558(3) BGB. Please give your consent no later than the expiry of [date + 2 months from receipt] by returning a signed copy or by making the first payment of the new rent on time. Kind regards [landlord's name]

How Rentprime helps you

Rentprime has a Rent-increase assistant: you select the flat, the system automatically checks the 15-month interval and the capping limit (15 or 20% depending on the region), proposes the maximum permissible increase, retrieves the rent-index value (from Q3 2026 for 80 cities) and generates the legally sound rent-increase letter — ready to send directly by registered post with proof of delivery. Consent deadlines are automatically flagged in the calendar.

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