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The rule in one sentence
Under the law of 21 September 2006 on residential leases, the annual rent of a dwelling may not exceed 5% of the capital invested in it. Divide that by twelve and you have the maximum monthly rent, charges excluded.
A worked example makes the scale clear. If the capital invested in a flat is €600,000, the maximum annual rent is €30,000, or €2,500 a month. If the capital invested is €400,000, the ceiling is about €1,667 a month.
The reform of August 2024 did not change the 5% itself. It did remove two elements that used to complicate things: the category of "luxury housing" that could escape the cap, and the requirement to state the capital invested in the lease.
What "capital invested" means
The capital invested is not the market value of the property, and it is not the price you might see on a listing today. It is, broadly, what was actually spent to acquire and build the home, plus the cost of later improvements, updated over time.
According to the Housing Ministry's guidance, the calculation works like this:
- The starting point is the price paid for the land and the construction, including related costs and later improvement works, documented by invoices and deeds.
- That amount is revalued using official coefficients, so that money spent years ago is expressed in today's terms.
- For buildings more than fifteen years old, a depreciation of 2% a year applies, unless the owner can document the maintenance work that keeps the building's value.
Two things follow. A flat bought recently at a high price usually has a high capital invested, and therefore a high ceiling. An older building bought decades ago, with little documented renovation, can have a ceiling well below today's market rent. That gap is exactly why the rule matters more for some tenants than for others.
Worth knowing. Only the rent commission of the commune and the courts can validate a calculation of capital invested. A landlord's own figure, or a tenant's estimate, is a starting point for discussion, not a legal fact.
How often rent can change
The law also frames how rent moves during a tenancy.
- Rent can be adjusted at most every two years.
- Each adjustment is capped at 10%, and the result must still respect the 5% ceiling.
- Indexation clauses that tie rent automatically to the cost-of-living index are not allowed in ordinary residential leases.
So a landlord who wants to raise the rent needs to wait two years from the start of the lease or the last adjustment, and cannot jump by more than a tenth in one step. A tenant who receives a larger or more frequent increase has good grounds to refuse it in writing.
Furnished homes
A furnished rental may carry a supplement on top of the rent calculated from the capital invested. The Housing Ministry describes it as a maximum of 1.5% a month of the invoice value of the furniture, counting only furniture bought within the previous ten years. The supplement stays fixed unless furniture is replaced, and it can be reviewed every two years.
In practice, ask for the split between the rent for the dwelling and the furniture supplement. It clarifies what you are paying for, and it matters for the deposit, which is calculated on the rent.
How a tenant can check the figure
Here is the realistic sequence if you think your rent is above the legal ceiling.
1. Ask for the basis in writing
Write to your landlord asking how the rent was set and what the capital invested is. There is no longer an obligation to state it in the lease, but a landlord confident in the figure will usually explain it.
2. Estimate for yourself
Look at when the building was constructed and what similar homes sold for at that time. The result will be rough, but it tells you whether you are talking about a small difference or a large one.
3. Go to the rent commission
Every commune has a commission des loyers. It is the mandatory first step in rent disputes: it hears both parties, determines the capital invested where needed, and tries to reach a compromise. Applications go through the municipal administration, generally within one month of the written disagreement.
4. Go to court if necessary
If one party does not accept the commission's decision, the justice of the peace can hear the case. For most tenants, the commission stage resolves things.
Should you actually do this?
Honestly, it depends. If you rent a recently built flat, the capital invested is probably high and your rent is likely within the ceiling even if it feels expensive. If you rent in an older building that has not been renovated in years and your rent is at the top of the market, the question is worth asking.
Timing matters too. Raising the issue at the start of a lease is easier than two years in, when a relationship with the landlord exists. And a tenant who knows the rules is in a stronger position when the next increase is proposed, even without ever going to the commission.
The rule may change
The 5% rule has been criticised for years, both because the capital invested is hard to establish and because it bears little relation to current prices for older homes. In April 2026 the Housing Minister and members of parliament examined research from LISER and the Housing Observatory on possible new methods, including revaluing capital in line with actual price trends. At the time of writing this is preparatory work, not law. We will update this guide if the calculation changes.
Our take
The rent cap is not a tool most tenants will use, but it is one every tenant should understand. It explains why rents move in steps every two years, why indexation clauses are not valid, and why an older flat can sometimes be challenged. If you are comparing rooms or apartments, our guide to what renting actually costs and our current listings are the practical next step.
Sources
This article explains the general framework of Luxembourg residential lease law and is not a substitute for legal advice on your individual contract. For official procedures and current forms, consult guichet.lu or your commune.
