What is it and when to do it?
The Mietkaution is a security deposit that protects the landlord against damage or unpaid rent. Its maximum amount is set by law (§ 551 BGB): no more than three net cold rents. It is paid before or on move-in and can be split into three instalments.
Where and how much does it cost?
Pay by bank transfer to the landlord’s account, or use a specialist product: a Mietkautionskonto (your account, your money) or a Mietkautionsbürgschaft instead of cash.
Common mistakes
- Cash with no paper trail. Always transfer: the bank statement is your only proof that the deposit was paid.
- More than three months’ cold rent. Anything above the § 551 BGB limit is unenforceable, even if you signed it.
- Paying the full amount when you can’t afford it. The right to three equal instalments is yours; the landlord cannot refuse.
- Waiting quietly after you move out. If six months pass with no money and no explanation, send a written demand with a deadline.
Alternative: a Guarantee Instead of a Cash Deposit
With a Mietkautionsbürgschaft an insurer vouches for you: the landlord gets the same security and your money stays with you. Providers include kautionsfrei.de↗ (the company plusForta) and Deutsche Kautionskasse↗ with its Moneyfix product.
What matters is knowing what you pay for. The fee is a percentage of the deposit per year — roughly 4.5–7% across the market (kautionsfrei publishes 5.25% a year, minimum €50). On a €1,500 deposit that is about €79 a year, or roughly €237 over three years of tenancy — money you never see again. A cash deposit, by contrast, comes back in full: under § 551(3) BGB the landlord must hold it in a separate interest-bearing account and the interest belongs to you (modest as it currently is).
In short: the guarantee solves “I don’t have €2,000 right now”, not “this is too expensive”. If you can raise the deposit, paying cash costs you less.