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How to deduct 100% of your mortgage interest in Luxembourg
Bought your home after 2023? You may be able to deduct all your mortgage interest with no cap. Here's how the new rules work and what to claim on taxx.lu.
If you bought your home recently, there's a good chance you can deduct every single euro of mortgage interest you paid this year. No cap. No limit. The full amount.
Sound too good to be true? It's not. It's the law. And since the 2024 tax year, the rules have changed in a way that makes this even more accessible than before.
Here's how it works, who qualifies, and what to watch out for.
The new rules: date of availability, not move-in date
Until recently, the deductible ceiling for mortgage interest in Luxembourg was based on when you moved into your property. That's no longer the case.
Since the 2024 tax year, the key criterion is the date of availability of your property. That's the date when your home was ready to be lived in, even if you actually moved in later.
This matters because it changes which deduction limit applies to you. And for recent buyers, the news is very good.
The deduction limits at a glance
The amount of mortgage interest you can deduct depends on when your property became available. The limit applies per person in the household: you, your spouse or partner, and each dependent child.
| Date of availability | Deductible limit per person per year |
|---|---|
| After 31/12/2023 | Full deduction (no cap) |
| Between 01/01/2020 and 31/12/2023 | €4,000 |
| Between 01/01/2015 and 31/12/2019 | €3,000 |
| Before 01/01/2015 | €2,000 |
That top row is the headline: if your property became available after December 31, 2023, there is no cap on how much mortgage interest you can deduct. Every euro of interest goes straight off your taxable income.
What this looks like in practice
Patrick is married with two children. They moved into a new off-plan property in 2024. He paid €30,000 in mortgage interest that year. Because his property became available after 31/12/2023, he can deduct the full €30,000 on his tax return.
For older properties, the ceiling is per person and per year. A couple with one child whose property became available between 2020 and 2023 can deduct up to €12,000 per year (€4,000 x 3). A single person with a property available before 2015 is limited to €2,000.
Another example
Mia is in a civil partnership with one child. Their property became available in 2009. Her limit is €2,000 per person, or €6,000 for the household. She paid €8,000 in interest in 2024. She can deduct €6,000. The remaining €2,000 is not deductible.
What counts as the "date of availability"?
This is where it gets specific, and where getting it right matters.
The date of availability is the date when your property was actually ready to be lived in. That depends on how you acquired it:
Ready-to-move-in property: The date of availability is the acquisition date, even if you do some light cosmetic work (painting, new flooring) before moving in.
Off-plan purchase (VEFA): The date of availability is the handover of the turnkey property, when the developer gives you the keys to a finished home.
Full renovation of an old and uninhabitable property: The date of availability is when the renovation is complete and the property becomes habitable (heating, sanitary facilities, kitchen, and sufficient living space).
Previously rented properties
If you bought a property you were previously renting, the date of availability is the date it became habitable for you as the owner, not the date you started renting it.
For properties occupied before 2022, you indicate the move-in date. For properties available after 2023, you indicate the actual availability date. The distinction matters because it determines which row of the table above applies to you.
Properties under construction: unlimited deduction during the build
Here's a detail that many people miss. If your property is under construction or being renovated and you're not yet living in it, there is no cap on the deduction of interest during the construction period.
Once the property becomes available and you move in, the standard limits apply based on the availability date. But until that point, all interest paid on the mortgage is fully deductible.
The year of acquisition: extra deductions
In the year you buy your main residence, and only that year, you can also deduct:
- Notary fees related to the opening of the mortgage (not the deed of sale)
- Bank commission fees for setting up the loan
These are one-off costs that can add up to several thousand euros, and they're often forgotten.
Don't confuse the invoices
The deductible notary fees are for the "credit opening" (ouverture de crédit), not for the deed of sale. The deed of sale includes registration fees, which are not deductible. Make sure you have the right invoice.
No retroactive deduction
If you forgot to claim these costs in your year of acquisition, you can't go back and claim them on a later return. It's that year or never.
What about property abroad?
If you're a cross-border worker or a resident with a main residence outside Luxembourg, you can still deduct mortgage interest. But the mechanism is different.
Property in Luxembourg: The interest directly reduces your taxable income. Straightforward.
Property abroad: The interest doesn't reduce your taxable income directly. Instead, it's used to adjust your overall tax rate, which is then applied to your Luxembourg income. The result is still a lower tax bill, but the calculation works differently behind the scenes.
In both cases, the same deduction limits apply.
Cross-border workers: don't forget assimilation
To claim mortgage interest deductions as a non-resident, you need to qualify for tax assimilation. That means at least 90% of your household income comes from Luxembourg, or your household earns less than €13,000 net abroad, or (for Belgian residents) more than 50% of professional income is earned in Luxembourg. taxx.lu automatically checks your eligibility.
What is NOT deductible
It's worth being clear about what you can't claim, because these are common misconceptions:
- Rent. If you're a tenant, your rent is not deductible.
- Property tax. Don't include it in your tax return.
- Maintenance and renovation costs. Repairs, improvements, and upkeep costs for your main residence are not deductible, even if they're significant.
- The deed of sale. Registration fees and the notary invoice for the purchase itself are not deductible (only the credit opening invoice is, and only in the year of acquisition).
- Interest on a second home or holiday property. This falls under "special expenses" with a much lower ceiling, not under the main residence category.
How taxx.lu makes it easy
Mortgage interest deductions involve several moving parts: the availability date, the per-person calculation, the year-of-acquisition extras, the difference between Luxembourg and foreign properties. Getting it wrong means either leaving money on the table or claiming too much and facing issues later.
taxx.lu handles all of this for you.
Automatic calculations. Enter your mortgage details and taxx.lu applies the correct limits based on your availability date, household composition, and whether the property is in Luxembourg or abroad. No manual maths.
Year-of-acquisition costs. taxx.lu prompts you for notary and bank fees in the relevant year so you don't miss these one-off deductions.
Mortgage interest simulator. Not sure whether your interest is fully deductible or capped? taxx.lu has a free simulator that tells you in seconds. No account needed.
Real-time refund estimate. See the impact of your mortgage interest deduction on your refund as you fill in your return. Every euro entered, every impact visible.
Try the mortgage interest simulator
Before you even start your return, you can use taxx.lu's free mortgage interest simulator to check whether your interest is fully deductible or capped. It's instant and requires no account. Go to the simulator
File your 2025 tax return now
The official ACD forms are available from April 7, but your 2025 tax return is already ready to fill in on taxx.lu. If you own your main residence, this is likely one of the biggest deductions on your return. Make sure you're claiming everything you're entitled to.
Creating an account is free. Running a simulation is free. You only pay when you're ready to download the final form.
If you bought after 2023, you can deduct 100% of your mortgage interest. Don't leave it on the table.
