Since tax year 2026, the deduction of mortgage interest no longer exists for let properties. On top of that, property tax is rising in several Brussels municipalities, and second-home taxes on the coast are still being challenged. The agency does not file its owners’ tax returns. It must still be able to explain these three topics and refer owners to an accountant or a tax adviser.

What has changed for the interest deduction?

The Act of 18 December 2025 laying down various provisions rewrites Article 14 of the 1992 Income Tax Code. It was published on 30 December 2025. Until then, an owner could deduct certain interest. It concerned debts « spécifiquement contractées en vue d’acquérir ou de conserver des biens immobiliers » (specifically incurred to acquire or keep real estate). This is recalled in the FPS Finance notes for 2024 income. Article 2 of the Act replaces that paragraph. The new text only covers « les redevances et la valeur des charges y assimilées » (fees and the value of similar charges). They relate to a long lease, a building right or a similar real estate right. Interest has disappeared from the article. Article 14 of the Act makes the change applicable « à partir de l’exercice d’imposition 2026 » (from tax year 2026), meaning 2025 income. It was thus published when that income year was almost over. It makes no exception for loans taken out before its publication.

How does the 2026 tax return reflect this?

The 2026 tax return form was set by a Royal Decree of 17 March 2026, published on 23 March 2026. The notes for 2024 income contained a heading for this interest, in box IX. It covered properties that had produced non-exempt real estate income. This heading no longer appears in the notes for 2025 income. They say it plainly: from tax year 2026, « la déduction ordinaire d’intérêts fédérale » (the ordinary federal interest deduction) no longer applies. The same list mentions the end of the federal housing bonus, of the reduction for home savings and of the one for green loans.

Where does the Constitutional Court challenge stand?

An action for annulment must be brought within six months of the publication of the law. This is Article 3 of the Special Act of 6 January 1989 on the Constitutional Court. For a law published on 30 December 2025, the deadline therefore ran until 30 June 2026. On 26 May 2026, a taxpayer challenged Article 2 of the Act of 18 December 2025. The case bears docket number 8670, according to the notice published in the Official Gazette. Other actions followed until 30 June 2026. The Court joined them to case 8670: they are numbers 8688, 8692, 8696, 8709, 8713 and 8722, according to a second notice. Action 8722 expressly targets Articles 2 and 14 of the Act. As of 14 October 2026, no extract of a judgment had been published in the Official Gazette in these cases.

An action does not suspend the law by itself: under Article 19 of the Special Act, suspension must be requested and granted by the Court. In practice, the deduction therefore remains abolished until the Court rules. Nobody can predict the outcome or its date today. That is the most honest message to give an owner who asks.

What does the end of the deduction change for the agency?

The agency does not calculate each owner’s tax: it depends on their whole personal situation. It is still on the front line when the question comes up. Four reflexes help to answer it:

  1. Talk about net yield: for a property financed with a loan, interest is still an expense, but it no longer reduces tax. The owner’s rent expectations may be affected.
  2. Recall the framework of the current lease: a new tax cost cannot be passed on freely to the tenant. For a current lease, the margin goes first through indexation, whose autumn 2026 rules are detailed here.
  3. Base the reletting rent on facts with market data. See our article on rents in the first half of 2026 in the three regions.
  4. Take care of the management report: rents collected, charges paid and fees appear separately. The owner’s accountant finds a working basis there. See our article on the management report owed to the owner.

For owners who let a large number of properties, another question may arise: that of the professional landlord under the Code of Economic Law. Here too, the agency refers them to an adviser.

Who pays the property tax on a let property?

Property tax is an annual regional tax calculated on indexed cadastral income. In Brussels, it is owed by the owner, possessor, long leaseholder, building right holder or usufructuary. The situation on 1 January counts, according to the Brussels Fiscality page. For a let dwelling, all three regions prohibit passing it on to the tenant, each in its own text:

Region Text Rule
Brussels Brussels Housing Code, Art. 226 Prohibited for main residence, student, shared and sliding leases
Wallonia Decree of 15 March 2018 on residential leases, Art. 59, 73 and 83 Prohibited for main residence, shared and student leases
Flanders Flemish Residential Lease Decree, Art. 36, § 1 Prohibited: « kan niet ten laste van de huurder worden gelegd »

Brussels adds an active obligation, in Article 226. Some households are entitled to a property tax reduction under Article 257 of the Income Tax Code. The landlord applies for it at the tenant’s first request, once the relevant information has been received. The household benefits « soit d’une réduction de loyer équivalente, soit d’un versement séparé ». That means an equivalent rent reduction or a separate payment. For the agency, this is a concrete task: receive the request, forward it and follow up the refund to the tenant.

Why is Brussels property tax rising in 2026?

In Brussels, the amount equals the indexed cadastral income multiplied by an overall rate, explains Brussels Fiscality. This rate adds the regional share of 1.25%, the agglomeration share of 12.3625% (989 additional centimes) and the municipal share. The municipal share depends on the centimes voted by each municipality: 3,850 in Anderlecht, or 48.125%. In the official example, a property in Anderlecht with an indexed cadastral income of 1,500 euros pays 926.10 euros. For 2026, the Region gives three reasons for the increase. The index stands at 2.3, which is 2.47% more than the previous year. Some municipalities have raised their additional centimes. Finally, the cadastral income may be revised after works. Two municipal examples are documented. Watermael-Boitsfort went from 3,090 to 3,390 centimes, according to the council decision of 16 December 2025. Saint-Josse-ten-Noode set 4,090 centimes for 2026, an increase the municipality presents as the first since 2002.

One point often surprises landlords. The BE HOME premium, 164 euros in 2026, requires being domiciled in the property. It therefore does not reduce the property tax on a let dwelling. An owner who compares the bill for their home with that of their let property sees a difference: this often explains it.

Where do second-home taxes on the coast stand?

Coastal municipalities levy taxes on second homes, and their legality is being argued all the way to the Court of Cassation. On 21 December 2023, the Court of Cassation dismissed the appeal of the municipality of De Panne (judgment F.22.0138.N). The court of appeal had held that permanent residents and second-home owners benefit equally from municipal services. There was therefore no reasonable ground to charge the cost to second-home owners alone. The Court of Cassation held that this decision was legally justified.

On 15 January 2026, two judgments ruled differently for Knokke-Heist (F.23.0106.N) and Koksijde (F.24.0048.N). Their regulations call the tax a « forfaitaire weeldebelasting op het gebruik van een luxegoed ». It is a flat-rate tax on the use of a luxury good. According to the Court, some assumptions are not unreasonable. A dwelling without registration in the population register is, as a rule, a second property. Its holders then, as a rule, have sufficient means. The Ghent court of appeal required proof that every taxpayer has sufficient means: wrongly so. The two appeal judgments are quashed, in whole or in part. The cases go to the Antwerp court of appeal, which must rule again.

The lesson for an agency is simple: everything depends on the justification written in each municipal regulation. As the Court describes them, both regulations target a dwelling that serves as main residence neither for the owner nor for the tenant. A dwelling where nobody is registered in the population register on 1 January is presumed to be in that case. For a property let year-round to a domiciled tenant, the question therefore arises differently than for a seasonal let. An agency managing on the coast can keep the tax assessment notices, lease dates and proof of payment. It refers any challenge to a lawyer or tax adviser.

How does Seido help report to the owner?

Do you manage several properties? In Seido, the management report details each expected and collected rent with its status. It also covers the property’s charges, your fees, the interventions and their cost. Indexations and service charge settlements appear in an appendix. The owner receives it as a PDF, in their language, with no account to create. They thus have clear figures to hand to their accountant. See how automated owner reporting works.

Frequently asked questions

What should you tell an owner who asks what the reform costs them?

That the answer depends on their whole tax return, not only on the property managed by the agency. The agency can give them the figures it knows: rents collected, charges paid, fees, works. It can also remind them of the verifiable facts: the Act of 18 December 2025, tax year 2026 and the pending action under number 8670. Calculating the tax and choices in the return are a matter for their accountant or tax adviser. The agency refers them there explicitly.

Does the Constitutional Court action suspend the abolition?

No. Under Article 19 of the Special Act of 6 January 1989, the Court may suspend a challenged law. This requires a request from the applicant and a reasoned decision. The notices published in the Official Gazette for cases 8670 and 8722 concern actions for annulment. The notes for the 2026 tax return state that the ordinary federal interest deduction no longer applies. Until the Court has ruled, that is the regime that applies.

Can the lease make the tenant pay the property tax?

Not for a main residence lease, in any of the three regions. In Brussels, Article 226 of the Housing Code also covers student, shared and sliding leases. In Wallonia, the 2018 decree repeats the prohibition for main residence, shared and student leases. In Flanders, Article 36 of the Residential Lease Decree prohibits it for the let property. A contrary clause therefore does not allow this charge to be recovered from the tenant.

Is a flat let year-round on the coast a second home?

It depends on the municipality’s regulation. As described by the Court of Cassation, the Knokke-Heist and Koksijde regulations target a specific type of dwelling. It serves as main residence neither for the owner nor for the tenant. They rely on the absence of registration in the population register on 1 January. A tenant domiciled in the property therefore changes the picture, whereas a seasonal let remains covered in principle. Always check the text of the regulation for the year concerned.

Sources and references

Last updated: October 2026. This article is provided for information purposes only and constitutes neither legal advice nor tax advice. For any specific situation, consult an accountant, a tax adviser or a lawyer.