Mietkaution: how much is allowed? (2026)

What is the Mietkaution?

The Mietkaution (security deposit) is security you give the landlord at the start of the tenancy. It covers possible claims — unpaid rent, owed Nebenkosten (operating costs) or damage beyond normale Abnutzung (normal wear and tear). As long as none of that arises, you get the Kaution back in full after you move out.

The essentials first: the Kaution is capped by law, you do not have to pay it all at once, and the money economically remains yours. The rules are in § 551 BGB and protect you as the tenant.

How high can the Kaution be? (§ 551 Abs. 1 BGB)

For residential lets, the Mietkaution may be at most three Nettokaltmieten (§ 551 Abs. 1 BGB). The Nettokaltmiete is the pure rent for the flat — excluding operating and heating costs (Nebenkosten). What counts is therefore not the Warmmiete (rent including costs) but only the rent component without Nebenkosten.

A simple worked example:

Item	Amount
Nettokaltmiete	€800
Nebenkosten (advance payment)	€200
Warmmiete	€1,000
Maximum permitted Kaution (3 × Nettokaltmiete)	€2,400

The Kaution here is 3 × €800 = €2,400 — not based on the Warmmiete of €1,000. A deposit tied to the Warmmiete would be too high.

Can I pay the Kaution in instalments? (§ 551 Abs. 2 BGB)

Yes. You may pay the Kaution in three equal monthly instalments (§ 551 Abs. 2 BGB). The first instalment is due at the start of the tenancy, the other two with the following rent payments. On a €2,400 Kaution you therefore pay three times €800.

This right is guaranteed by law. The landlord may not exclude it in the lease, and may not make handover of the flat conditional on you paying the full sum upfront. A clause such as "the Kaution must be deposited in full before move-in" is void to that extent.

Achtung: You never owe more than three Nettokaltmieten. If the lease demands a higher Kaution — for example four months' rent, or a deposit based on the Warmmiete — the agreement is void for the excess (§ 551 Abs. 1 and 4 BGB). You can reclaim any part you overpaid, and you do not have to pay the excessive portion in the first place.

Where must the landlord hold the Kaution? (§ 551 Abs. 3 BGB)

The landlord must hold a Barkaution (cash deposit) separately from their own assets — on a separate account, not their private account (§ 551 Abs. 3 BGB). This protects your money if the landlord becomes insolvent: it does not fall into their insolvency estate.

The deposit must also earn interest (Verzinsung), customarily at the rate for savings deposits with three months' notice. The interest belongs to you and increases the Kaution — you get it back at the end together with the deposit. If the landlord does not invest the Kaution properly, or not at all, you can still claim the interest that would have accrued with correct investment.

What forms of Kaution are there?

The Kaution does not have to be cash. Three forms are common — the cap of three Nettokaltmieten applies to all of them:

Form	How it works	For you
Barkaution / Kautionskonto	You pay money; the landlord holds it separately and with interest (§ 551 Abs. 3 BGB)	Cash is tied up but earns interest; the interest is yours
Mietkautionsbürgschaft	A bank or insurer guarantees the sum for a fee	No capital tied up, but an ongoing fee
Verpfändung of a savings account	You pledge your own savings book in the landlord's favour	The money stays in your account and earns interest

Which form applies is agreed with the landlord. You can offer a particular form, but there is no statutory right to a specific one.

Common mistakes

• Calculating the Kaution from the Warmmiete. The basis is solely three Nettokaltmieten, not rent including Nebenkosten.
• Paying the full sum at once when instalments are due. You can always use your right to instalments under § 551 Abs. 2 BGB.
• Accepting an excessive Kaution. You do not have to pay more than three Nettokaltmieten — the excess is void.
• Not asking where the Kaution is held. You are entitled to a separate, interest-bearing investment and may demand proof.

For how you get the Kaution back at the end of the tenancy — including the Prüffrist (review period) and interest — see the guide Reclaiming your Kaution.

Mit HausMaus geht das einfacher

HausMaus keeps a Kaution tracker (§ 551 BGB) for you: it records how high your Kaution is, what you have paid in, who holds it and on what type of account, and what interest accrues. So what was agreed is documented from the start — and at move-out the Kaution is easy to reclaim in full. All the records sit alongside your Mietakte (rental file) in the document vault. For tenants, HausMaus is free.

See pricing – 1 % of collected rent, free for tenants →