Mängelanzeige & Repairs: Landlord Duties 2026

What do Mängelanzeige and the repair duty mean?

If a defect appears in the flat during the tenancy, the tenant must inform you "unverzüglich" (without undue delay) under § 536c BGB – this is the Mängelanzeige (defect notice). That notice triggers your duty: under § 535 Abs. 1 S. 2 BGB you must maintain the rental property in a condition fit for the agreed use – that is, fix the defect.

The load-bearing fact: your maintenance duty does not depend on whether the repair is "worth it". As long as a defect impairs use, you owe the repair – and promptly. If you do not respond within a reasonable time, the rent is reduced automatically (§ 536 BGB) and the tenant may have the defect fixed at your expense (§ 536a Abs. 2 BGB).

When exactly must you repair? (§ 535 Abs. 1 S. 2 BGB)

Your principal duty under the Mietvertrag (tenancy agreement) is to provide use and maintain the flat for the entire tenancy (§ 535 Abs. 1 S. 2 BGB). A Mangel (defect) exists where the actual condition deviates from the contractually owed condition to the tenant's disadvantage and impairs use more than just negligibly.

Exceptions to your duty are narrow:

• Damage the tenant caused themselves – the tenant is liable, not you.
• Validly transferred Kleinreparaturen – only with a valid Kleinreparaturklausel (minor-repair clause) carrying a per-repair and annual cap does the tenant bear small trivial costs.
• Mere inconvenience without impairment of use – not a defect.

Achtung: If you ignore the Mängelanzeige because you consider the defect minor or the repair uneconomical, you risk the full set at once: ongoing Mietminderung (§ 536 BGB), Aufwendungsersatz after Selbstvornahme (§ 536a Abs. 2 BGB), and the tenant's Zurückbehaltungsrecht (right to withhold) over the remaining rent. The reduction runs until the defect is fixed.

What deadline applies – and when do you fall into Verzug?

There is no fixed statutory deadline. It must be angemessen (reasonable) and depends on the nature and urgency of the defect. If the tenant set you a reasonable deadline and you let it lapse, you fall into Verzug (default) – which opens Selbstvornahme (self-remedy) under § 536a Abs. 2 Nr. 1 BGB.

Urgency of defect	Example	Reasonable deadline (practice)
Acute danger / emergency	burst pipe, heating failure in winter, power outage	24–48 hours, immediate in an emergency (§ 536a Abs. 2 Nr. 2 BGB: no deadline)
Serious impairment	mould, broken boiler, leaking window	1–2 weeks
Normal repair	dripping tap, jamming door	2–3 weeks
Minor defect	cracked tile, small plaster damage	up to 4 weeks

A key distinction: no deadline is required for Mietminderung under § 536 BGB – it takes effect automatically as soon as a significant defect exists and has been reported. A deadline is only needed if the tenant wants to have the defect fixed themselves and claim the cost from you (§ 536a Abs. 2 Nr. 1 BGB).

What can the tenant do if you do not repair?

1. Mietminderung (§ 536 BGB) – the rent is reduced by operation of law once the significant defect is reported. No deadline is needed for this.
2. Selbstvornahme + Aufwendungsersatz (§ 536a Abs. 2 BGB) – after a reasonable deadline lapses without result (Nr. 1), or in an emergency without a deadline (Nr. 2), the tenant may have the defect professionally fixed and claim the necessary costs from you.
3. Zurückbehaltungsrecht (§ 320 BGB) – on top of the reduction, the tenant may withhold part of the ongoing rent as leverage until you repair. The courts generally cap the withholdable amount at three to five times the monthly reduction amount (cf. BGH, judgment of 17.06.2015, Az. VIII ZR 19/14). Unlike the reduction, the withheld amount is paid back after the repair.
4. Schadensersatz (§ 536a Abs. 1 BGB) – damages, on fault or an initial defect.
5. Termination without notice (§ 543 Abs. 2 Nr. 1 BGB) – if the agreed use remains denied in whole or to a significant degree.

Handling a Mängelanzeige correctly: step by step

1. Document receipt – note the date and content of the notice. Your response deadline starts on receipt.
2. Classify the urgency – emergency, serious, or minor? Your deadline follows from that (see table).
3. Respond fast – confirm receipt and announce concrete steps. Silence is the most expensive mistake.
4. Engage a Handwerker – book an appointment promptly; immediately for emergencies.
5. Document the repair – keep the order, the invoice, and the completion. This is your evidence against unjustified Mietminderung and for the end of the reduction period.
6. Inform the tenant – when the defect is fixed, so the reduction ends.

Common landlord mistakes

• Sitting out the notice. Silence leads to Verzug, ongoing reduction, and Selbstvornahme at your expense.
• Assuming a Mietminderung requires a missed deadline. Wrong – the reduction under § 536 BGB takes effect automatically with the notice.
• Shifting Kleinreparaturen without a valid clause. Without a valid Kleinreparaturklausel with caps, you bear even small repairs.
• Not documenting repairs. Without proof of the order and completion, you cannot limit the reduction period.
• Refusing Aufwendungsersatz outright. With a valid Selbstvornahme you owe the necessary costs – the only worthwhile dispute is over the amount, not whether you owe.

HausMaus makes this easier

In HausMaus, your tenants' Mängelanzeigen arrive centrally as Tickets – time-stamped, so your response deadline is cleanly documented. You assign each ticket straight to a Handwerker from your contact directory, upload the invoice to the case, and track the repair through to completion. That gives you a seamless record that you acted promptly – your best protection against Mietminderung and Selbstvornahme. Wohnen, geregelt. (Home, handled.)