In a referendum on 10 June 2018, the cantonal initiative “Tenant protection on moving in (YES at affordable new rents)” was adopted. With the decision of the Government Council of 18 September 2018, the Canton of Basel-Stadt declared the use of the form for notification of the initial rent for the conclusion of a new rent agreement for residential premises compulsory as of 1 November 2018 . This form must be used to disclose the rent paid by previous tenants. If the landlord fails to indicate the initial rent on the form within no fewer than 30 days before the tenant moves in, the term in the rental agreement on the amount of the rent shall be null and void. As a result, the court must supplement the rent agreement by setting an appropriate initial rent.