Challenging the initial rent: deadline, official form and procedure

The legal basis is Art. 270 of the Swiss Code of Obligations (CO). You can challenge the initial rent at the conciliation authority within 30 days of taking over the flat if one of two conditions is met:

• You signed the lease because of personal or family hardship, or because the local housing market forced you to. A housing shortage is assumed where the vacancy rate is very low, which has been the case in Zurich, Geneva, Basel, Lausanne and many suburbs for years.
• The landlord raised the rent substantially compared with what the previous tenant paid for the same flat. According to the Federal Supreme Court, an increase of more than 10 percent counts as substantial.

Filing the challenge does not lower the rent by itself. The conciliation authority checks whether the rent is abusive: whether it gives the landlord an excessive return (Art. 269 CO) or exceeds what is customary in the neighbourhood for comparable flats (Art. 269a CO).

Cantons with a housing shortage may require landlords to hand over an official form with every new lease (Art. 270 para. 2 CO). It states the previous rent, the new rent, the reason for any increase and how to challenge it. Since 2025 the form must also state the reference interest rate and the inflation figure the previous rent was based on.

The form is mandatory in, among others, the cantons of Zurich, Geneva, Basel-Stadt, Fribourg, Lucerne, Zug and Nidwalden, since 1 December 2025 also in Bern, and in municipalities with a housing shortage in Vaud and Neuchâtel. The list changes; the cantonal housing office or the tenants' association knows the current state.

If the form is missing where it is required, the agreement on the rent is void. You can then ask the court to set the rent even after the 30 days and reclaim any overpayment. Do not wait years, though: anyone who knows of the defect and does nothing risks the accusation of abuse of rights.

1. 1

   Note the deadline

   The 30 days run from the day you take over the flat, that is from the handover of the keys, not from signing. What counts is when your request reaches the conciliation authority.

2. 2

   Gather documents

   Lease, the form or other evidence of the previous rent, the listing, photos of the flat and listings of comparable flats in the neighbourhood.

3. 3

   File the conciliation request

   The competent authority is the one where the flat is located. A simple letter is enough: parties, the flat, start of the lease, previous and new rent, and a request to set a lower rent. Many cantons offer an online form. The procedure is free of charge (Art. 113 Civil Procedure Code).

4. 4

   Hearing

   The authority summons both parties within roughly two months. Settlements are common. Otherwise it issues a proposed judgment or the authorisation to proceed.

5. 5

   Rental court

   If the dispute continues, you can take it to court within 30 days. If the court sets a lower rent, that applies retroactively from the start of the lease and the difference is refunded to you.

In the procedure the landlord has to disclose what justifies the rent. In a yield calculation, the net yield may exceed the reference interest rate by at most 2 percentage points as long as that rate is 2 percent or lower. At the current 1.25 percent this means 3.25 percent on the equity invested. For older buildings with low investment costs, the permissible rent is often well below what is being charged.

The risk is manageable. Conciliation is free; the rental court may charge court fees depending on the canton. Retaliatory notice can be contested: during the proceedings and for three years afterwards, the landlord cannot terminate the lease if you won in full or in part or if you reached a settlement (Art. 271a CO).

• Missing the deadline. The 30 days are strict and cannot be extended.
• Complaining to the landlord only. The challenge has to reach the conciliation authority.
• Cutting or withholding rent in protest. Being in arrears is grounds for notice (Art. 257d CO). Pay in full during the proceedings.
• Not demanding the form although it is mandatory in the canton.
• Not saving comparable listings. What is online today is gone in three months.