Giving notice
Ending a lease, on the right date
As a tenant you give three months' notice to the end of a month, and you need no reason. What decides the date is when your notice arrives: on or before the third working day of a month, that month counts; after it, everything shifts by one month. The notice must be on paper and signed, an email does not meet the legal form.
Three months, and the third working day
§ 573c BGB gives tenants a three-month notice period, regardless of how long they have lived there, always ending at the end of a calendar month. Landlords face longer periods the longer a tenancy has run; tenants do not.
The cut-off is the third working day of the month. If your notice arrives by then, the lease ends at the close of the month after next. If it arrives later, that month no longer counts and the end shifts by a further month. A notice arriving on 2 October ends the lease on 31 December; the same notice arriving on 6 October ends it on 31 January.
What counts is arrival at the landlord, not the date you wrote or the postmark. Saturdays count as working days, Sundays and public holidays do not. If the date matters, send it by registered delivery and keep the tracking number.
The form: paper, signed by hand
Terminating a residential lease requires written form under § 568 BGB: printed, signed by hand, delivered as an original. An email, a message in a portal or a scan does not satisfy it.
If several people are named in the contract, all of them have to sign. One flatmate cannot leave a joint contract alone; that needs an agreement with the landlord.
Many landlords accept an email in practice and confirm it. That is their goodwill, not your right. When the date matters, follow up with the original.
Fixed terms and waivers
Not every contract is open-ended. A genuine fixed-term lease under § 575 BGB requires a reason stated in the contract, such as the owner's own use afterwards. Without such a reason the contract counts as open-ended and you can give notice normally. During a valid fixed term, ordinary notice is generally not possible for either side.
Also common is a mutual waiver of the right to give notice for one or two years. It is permitted within limits, and it binds you as well as the landlord. Read the contract for this clause before signing, because it decides whether you can leave after six months.
The replacement-tenant myth
There is no general right to leave early by presenting a replacement tenant. The landlord does not have to accept them. Only in genuine hardship, a job moving you across the country or a care situation, can such a claim arise, and even then the candidate must be reasonable.
In practice it often works anyway, because it suits the landlord too. Ask early, propose two or three candidates and get the agreement in writing. Without written consent your contract continues, even if someone else has already moved in.