Why report it in writing
As a tenant you must tell your landlord about defects without delay (§ 536c BGB). If you don't, you can lose the right to reduce the rent and may have to pay for damage that gets worse. A letter is easy to prove later, unlike a phone call.
What to write
- Describe each defect precisely: where it is, what is wrong and since when. One defect per line.
- Set a reasonable deadline for the repair, usually about two weeks. For urgent problems, like no heating in winter or water coming through the ceiling, call the landlord or the emergency number right away and set a much shorter deadline.
- Keep photos with the date and any messages about the defect.
Rent reduction
If a defect noticeably affects how you can use the flat, the rent is reduced by law for that time (§ 536 BGB). How much depends on the defect and is often disputed. The letter therefore says that you pay the rent only under reservation (unter Vorbehalt) and reserve a reduction. Don't simply stop paying: ask your local tenants' association (Mieterverein) or a lawyer before you reduce the rent yourself.
How to send it
Sign the letter and send it so that you can prove it arrived: by registered mail (Einwurf-Einschreiben) or hand it over in front of a witness. Keep a copy.