Further to the comments above, a tenancy agreement entered into for an unlimited period may be terminated by way of an ordinary termination (i.e. by serving notice of the minimum contractual or statutory periods of 3 or 6 months) or by way of an extraordinary termination (i.e. without observing termination periods or dates). The prerequisites for an extraordinary termination are provided for in law. If these are not met, such a termination is invalid.
If the lessor gives notice of termination, he is required to use an official form. The tenant is to terminate in writing. Special regulations apply in the case of terminating a family residence.
In other respects, the tenant may also return the rented property prematurely (i.e. without adherence to the termination periods and dates). In this respect the lessor is under obligation to take back the rented premises. As a general rule, the tenant is liable up until the end of the limited tenancy or the next possible date on which the tenancy can be terminated. The tenant is released from the liability if he proposes that the lessor take on an acceptable and solvent replacement tenant who is willing to enter into the tenancy agreement at the same conditions.