Shared flat and subletting: when can I sublet? (2026)

Subletting: your claim to permission

For part of your dwelling, you as a tenant have a claim to permission to sublet. This is set out in § 553 Abs. 1 BGB: if a berechtigtes Interesse (legitimate interest) arises after the rental contract is signed in handing over part of the dwelling to a third party, you may demand permission from the landlord. You are not merely hoping for a yes — you have an enforceable claim.

The key distinction is part versus whole. For part of the dwelling, the claim to permission under § 553 BGB applies. The entire dwelling may only be handed over with the landlord's express consent (§ 540 BGB) — there is no statutory claim to that.

What is a berechtigtes Interesse?

The berechtigtes Interesse (legitimate interest) must have arisen after the contract was signed and carry some weight. Recognised reasons include:

• the wish to lower your rent burden by subletting a room;
• a partner or WG (shared-flat) flatmate moving in;
• a longer work- or study-related stay in another city or abroad while you keep the flat;
• forming or expanding a Wohngemeinschaft (shared flat, "WG").

Economic or personal reasons of some weight are enough. Mere convenience does not qualify, but a concrete financial or life-related reason certainly does.

When may the landlord refuse?

The landlord may refuse permission only for good cause (§ 553 Abs. 1 Satz 2 BGB), namely where

• there is an important reason in the person of the third party (for example serious past breaches),
• the dwelling would become overcrowded, or
• the handover is otherwise unreasonable for the landlord.

If the landlord refuses permission without justification, you may terminate the tenancy extraordinarily with the statutory notice period (§ 540 Abs. 1 Satz 2 BGB) — provided the important reason does not lie in the person of the third party.

Untermietzuschlag: when is an increase allowed?

If the handover is only reasonable for the landlord with an appropriate rent increase, the landlord may make permission conditional on your agreeing to an Untermietzuschlag (subletting surcharge) (§ 553 Abs. 2 BGB). In practice, surcharges of roughly 10 to 20 percent of the sublet rent are regarded as appropriate, to cover the increased wear. You do not have to accept a flat surcharge with no factual basis.

Important: If you sublet without permission, you breach the rental contract. The landlord can issue an Abmahnung (formal warning) and, in a repeated or serious case, terminate the tenancy — even without notice (§ 540, § 543 BGB). Always obtain permission in writing before the subtenant moves in, stating the subtenant's name and the start date.

WG: which contract models exist — and who is liable?

In a Wohngemeinschaft (shared flat), the contract form decides who is liable to the landlord for rent and damage.

Model	Who is the contracting party	Liability to the landlord
Single joint contract	All WG members as main tenants	Joint and several — each is liable for the full rent (§ 421 BGB)
Separate per-room contracts	Each person individually with the landlord	Only for their own rent, no joint and several liability
Main tenant + subtenants	Only the main tenant (subtenants via § 553 BGB)	Only the main tenant is liable to the landlord

Under a single joint contract, the landlord can demand the entire rent from one person if others fail to pay (Gesamtschuldner — joint and several debtors). That person must then recover the money internally from the flatmates. Under the main-tenant model, the main tenant alone bears the obligation — the subtenants have no contract with the landlord.

Common mistakes

• Subletting without permission. Even with a claim, you must assert it — the claim does not replace the actual permission.
• Handing over the whole flat and invoking § 553 BGB. The claim to permission covers only part; the whole needs consent under § 540 BGB.
• Not naming the subtenant. The landlord is entitled to know who is moving in. Permission "for an unknown person" need not be granted.
• Underestimating WG liability. Under a joint contract, an insolvent flatmate can cost you the full rent. Clarify the model before moving in.
• Trying to turn a profit. Profit-oriented (short-term) subletting generally does not establish a berechtigtes Interesse per BGH case law — the claim supports cost-sharing, not a business.

With HausMaus it's simpler

HausMaus is free for tenants and supports WG and Untermiete from the start. You send the landlord the request for permission required under § 553 BGB straight from the app and keep the name, start date and the reply clearly documented. For the WG, every flatmate keeps a clear view of their own share of rent and Nebenkosten (service charges), so there is never any doubt about who owes what.