There are strict requirements in the Civil Basic Code (BGB) that must be taken into account. Tenants are given time to consider whether or not to agree to the higher rent.
If the landlord agrees to the rent increase, the new, higher rent will be paid at the beginning of the third month after the landlord's announcement. If there is no supply of rental housing on reasonable terms in the area, it is allowed to increase by 15 percent. The trend on the housing market in many places is already a rental price of over 30 euros per square metre.