Description
Conny is a Berlin legal-tech company that checks for free whether a rent is above the German rent cap (Mietpreisbremse) and, if so, claims the reduction and the overpaid rent from the landlord as a registered debt collector, taking a fee only if it succeeds.
The Mietpreisbremse, in force since June 2015 under § 556d of the German Civil Code, limits rent on new leases in designated areas to 10 % above the local comparative rent. It applies in 13 of the 16 Länder and about 730 towns, including Berlin, Hamburg and Munich, was extended in July 2025 until the end of 2029, and was confirmed by the Federal Constitutional Court in January 2026. Conny GmbH is registered as a debt-collection service under the Legal Services Act. Its rent check takes about two minutes; after a mandate it sends the formal complaint (Rüge) to the landlord and, if needed, goes to court with partner lawyers, covering the litigation costs.
Conny says the fee is usually covered from the repayment claims and the landlord pays; in rare cases a minimum fee equal to six months of savings applies. Stiftung Warentest described an earlier model in which tenants paid five months of savings, and the property site jacasa reported in 2026 that tenants often assign all overpaid rent and sometimes part of the deposit.
Strengths
- The rent check is free and quick, and the tenant pays nothing if Conny fails.
- Conny carries the litigation risk and costs, so tenants don’t have to sue on their own.
- It is a registered debt collector, and the law it enforces was confirmed by the Constitutional Court in 2026.
Weaknesses
- The fee can be high: tenants may give up all overpaid rent, part of the deposit or a minimum of six months’ savings.
- It is a commercial company with a profit motive; tenants’ associations and free tools also help with the Mietpreisbremse.
- Claiming against a landlord can strain the relationship, and the cap only applies in designated areas.
Who it is for
Tenants in German cities with a rent cap, such as Berlin, Hamburg or Munich, who suspect their rent is too high and don’t want to handle the claim or the court case themselves.