Working in Spain while registered in Brussels: what happens to my Belgian tax return and Brussels abatement for income year 2025?
Working in Spain while registered in Brussels? For 2025, declare foreign salary and check abatement, room rental and Spanish residence risks before filing.
For income year 2025, assessment year 2026, working in Spain does not automatically cancel the Brussels registration duty abatement. The real issue is whether the Brussels property remains your genuine principal residence, and whether you are still Belgian tax resident. If you remain Belgian tax resident, your Spanish salary must normally be declared in Belgium as foreign professional income, even if treaty relief applies. The correct answer depends on the exact facts of the individual situation.
The figures below are illustrative and relate to income year 2025 / assessment year 2026, with a Brussels property bought in 2022 under the former Brussels abatement regime.
Why this is more than a Belgian tax return question
A person who owns a home in Brussels, remains registered there, starts working in Spain and rents out part of the Brussels property is not dealing with only one tax question.
There are several parallel issues:
Belgian tax residence;
possible Spanish tax residence;
the Belgium-Spain double tax treaty;
the Brussels registration duty abatement;
Belgian taxation of a room rental;
Spanish reporting obligations, including possibly Modelo 720;
the practical risk of creating inconsistencies between official registration and real life.
This is why the answer cannot be reduced to “I am still registered in Belgium” or “I work in Spain”. Both facts matter, but neither is decisive on its own.
Does working in Spain cancel the Brussels abatement?
No, working in Spain does not automatically cancel the Brussels registration duty abatement.
The risk comes from the principal residence condition. Under the Brussels abatement rules, the buyer must establish their principal residence in the property and keep it there for an uninterrupted period of 5 years from the date the principal residence was established.
For a purchase made in 2022, the former Brussels regime generally applied an abatement of €175,000, giving a maximum registration duty saving of €21,875. This should not be confused with the newer €200,000 / €25,000 regime, which applies under the reform from 1 April 2023.
In a typical 2022 purchase, the 5-year period may therefore run until sometime in 2027, depending on the exact date on which the buyer established their domicile or principal residence in the Brussels property.
If the tax administration considers that the property stopped being the buyer’s real principal residence before the end of the 5-year period, part of the abatement may become repayable.
Since the 2023 reform, repayment is in principle prorated according to the number of full years not yet completed, and this prorated approach appears also to apply to earlier abatements. For example, if the original benefit was €21,875 and only 3 full years of the 5-year period were respected, a 2/5 repayment would be around €8,750. If only 2 full years were respected, a 3/5 repayment would be around €13,125.
These figures are only indicative. The exact calculation depends on the starting date of the 5-year period, the date on which the condition is considered broken, and how the administration applies the facts.
Legal registration is useful, but it is not the whole test
Remaining registered in Brussels is helpful evidence, but it does not automatically prove that the Brussels home is still the real principal residence.
The administration may look at factual indicators such as:
where the person actually sleeps most of the time;
where the person works;
whether there is a rental contract abroad;
where the person’s professional and personal life is organised;
whether the Brussels property remains genuinely available and used as the main home;
whether the property is partly or fully occupied by someone else;
the number of days spent in Belgium and abroad.
If the Brussels property is still genuinely occupied as the main home and only one room is rented out, the abatement risk is more limited.
If, in reality, the person lives mainly in Spain and the Brussels registration is only formal, the risk becomes much higher.
Can renting out one room make the abatement invalid?
Renting out one room in the Brussels property does not, by itself, necessarily cancel the abatement.
The key question remains whether the owner still has their principal residence in the property. The rules do not normally prohibit renting out part of the property. But there is an important distinction:
if the owner genuinely still lives in the property as their main home and rents out only one room, the abatement position is generally easier to defend;
if the property is no longer the owner’s real main home, the room rental may become one of several facts showing that the Brussels residence is no longer genuine.
The practical evidence matters: travel records, days spent in Brussels, continued use of the home, utility use, personal belongings, insurance, administrative links and whether the tenant occupies only part of the property.
Belgian tax residence for income year 2025
For Belgian income tax, a person who remains registered in Belgium will often still be treated as a Belgian tax resident unless the facts show otherwise.
Belgian tax residence is based on the person’s domicile or centre of economic or patrimonial interests, assessed on the facts. Registration in the Belgian national register creates a rebuttable presumption of Belgian residence.
As a Belgian resident, the person must declare their worldwide income in Belgium. This includes foreign salary, even if the foreign salary is ultimately exempted in Belgium under a double tax treaty.
For income year 2025, a typical Belgian resident return may therefore need to include:
Belgian salary earned before leaving or before working abroad;
Spanish salary earned for work physically performed in Spain;
Belgian real estate information;
income or taxable elements linked to renting out part of the Brussels property.
The Spanish salary should not simply be ignored.
How is Spanish salary treated in the Belgian tax return?
If the work is physically performed in Spain for a Spanish employer, the salary will generally be taxable in Spain.
If the person is still Belgian tax resident for income year 2025, Belgium will normally require the Spanish salary to be declared as foreign professional income. Belgium should then normally apply treaty relief, often through exemption with progression.
This means the Spanish salary is not taxed again in Belgium as ordinary Belgian taxable salary, but it may still influence:
the Belgian tax rate applicable to other taxable income;
the final calculation of Belgian tax;
in some cases, local taxes.
For assessment year 2026, relating to income year 2025, the Belgian online deadline cited in the analysis is 15 July 2026 for ordinary cases and 16 October 2026 when the taxpayer files online and has “specific income”, including foreign professional income.
What if the person has actually left Belgium?
If the factual situation is that the person truly left Belgium and moved their principal residence to Spain in 2025, the Belgian procedure may be different.
In that situation, the person may need to regularise the departure with Belgium. The Belgian tax authorities indicate that when someone leaves Belgium and resides abroad, a special tax return may be required within 3 months after departure, and a non-resident tax return may later be required for Belgian-source income.
However, this should not be done mechanically.
A formal departure from Belgium before the end of the Brussels abatement’s 5-year period can be a strong indication that the Brussels property is no longer the principal residence. That could increase the risk of partial repayment of the abatement.
This is why the residence analysis and the abatement analysis should be done together.
Could Spain also treat the person as Spanish tax resident?
Yes. Spain may also consider the person tax resident.
Under Spanish domestic rules, a person is generally treated as Spanish tax resident if they spend more than 183 days in Spain during the calendar year, or if the main centre or base of their activities or economic interests is located in Spain.
Spain also treats residence status on a full calendar-year basis, not as a split-year status.
For 2025, the position may be unclear if the person worked in Spain for only part of the year. Even if the stay is below 183 days, Spain may still look at the centre of professional and economic interests.
For 2026, if the person remains in Spain for the full year and continues working there, Spanish tax residence becomes much more likely.
What if Belgium and Spain both claim tax residence?
If Belgium and Spain both claim that the person is tax resident for the same year, the Belgium-Spain double tax treaty must be used to resolve the conflict.
In practice, the treaty analysis generally looks at:
where the person has a permanent home;
where the centre of vital interests is located;
where the person habitually lives;
nationality;
if needed, a mutual agreement between tax administrations.
This can be difficult when the person has a home available in both countries: for example, an owned property in Brussels and rented accommodation in Spain.
The strongest practical factors are usually the day count, where the person actually slept, where the personal life is centred, and where the economic activity was mainly located.
How is the Brussels room rental taxed in Belgium?
The Belgian tax treatment depends on how the room is rented.
If the tenant is a private individual using the room only for private residential purposes, Belgium generally does not tax the landlord on the actual rent for the immovable part.
Instead, the taxable real estate income is based on the relevant part of the non-indexed cadastral income, prorated according to the part of the property rented out and the number of rental days. The tax authorities then calculate the taxable amount using the indexed cadastral income increased by 40%.
This means the landlord should identify:
the non-indexed cadastral income of the property;
the percentage of the property represented by the rented room and shared areas;
the number of days during which the room was rented;
whether the tenant uses the room privately or professionally.
If the tenant uses the room professionally, or if the lease allows professional use, the Belgian tax treatment can become much less favourable because actual rent may become relevant.
What if the room is rented furnished?
If the room is rented furnished, there is an additional movable-income element for the furniture.
The Belgian tax authorities indicate that, unless the rental agreement provides another split, 40% of the total rent is deemed to relate to furniture. From that furniture rent, a 50% lump-sum expense deduction can normally be applied. The resulting net movable income is generally taxed at 30%.
For example, with rent of about €900 per month, annual rent would be around €10,800.
If the room is furnished and no split is made in the agreement:
default furniture portion: 40% × €10,800 = €4,320;
lump-sum expense deduction: 50%;
net movable income: €2,160;
separate tax at 30%: about €648.
This is separate from the immovable-income calculation based on cadastral income.
The lease should be written and registered
For a Brussels residential lease, registration must generally be done within 2 months of signature. Registration is free and is the responsibility of the landlord.
Registering the lease does not itself create the tax liability. The rental income must be declared correctly regardless. But registration helps bring the arrangement into legal compliance and clarify the private residential nature of the letting.
A properly drafted agreement should state:
whether the room is furnished;
the split between immovable rent and furniture rent, if relevant;
whether charges are included or separate;
the exact rented room and access to common areas;
that the tenant may not use the room for professional purposes;
that the tenant may not deduct the rent as a professional expense.
Spanish tax return, Modelo 720 and inbound worker regime
If the person is Spanish tax resident for 2025, Spain will generally require them to declare worldwide income, including foreign income, subject to treaty relief mechanisms.
That may include:
Belgian salary;
Belgian real estate;
Belgian room rental income.
For the Spanish 2025 income tax return, the campaign dates cited in the analysis are 8 April to 30 June 2026.
There may also be a Spanish foreign-asset reporting issue. If a Spanish tax resident owns real estate outside Spain above the relevant threshold, the Belgian property may trigger a Modelo 720 obligation. The analysis cites a €50,000 threshold for foreign assets, including foreign real estate.
For 2025, the official Modelo 720 filing period cited in the analysis was 1 January to 31 March 2026. If the first Spanish tax-residence year is instead 2026, the relevant Modelo 720 filing would normally arise in early 2027.
A further planning point may be the Spanish special regime for inbound or displaced workers. The analysis refers to Form 149 and a 6-month deadline from the start of activity for the main taxpayer to opt into the regime. Eligibility cannot be assumed and should be checked with a Spanish tax adviser.
What should be checked before filing?
Before filing the Belgian 2025 return, a person in this situation should normally clarify:
whether they are still Belgian tax resident for income year 2025;
whether Spain may also consider them tax resident;
the number of days spent in Belgium and Spain;
whether the Brussels home remained the real principal residence;
whether the Spanish salary must be declared in Belgium with treaty relief;
how the Brussels room rental should be declared;
whether the room was furnished;
whether the lease is registered and drafted correctly;
whether Modelo 720 or Spanish income tax filing obligations apply;
whether deregistering from Belgium could affect the Brussels abatement.
The most important point is consistency. A person cannot safely maintain one position for the Brussels abatement and another incompatible position for income tax without evidence.
Frequently asked questions
Does working in Spain automatically make me lose the Brussels abatement?
No. Working in Spain does not automatically cancel the Brussels registration duty abatement. The key question is whether the Brussels property remains your genuine principal residence during the 5-year commitment period.
Do I have to declare my Spanish salary in Belgium if I am still registered in Belgium?
Usually yes. If you are Belgian tax resident for income year 2025, you must normally declare worldwide income, including Spanish salary, even if Belgium later grants treaty relief.
Will Belgium tax my Spanish salary again?
Not necessarily. If the salary relates to work physically performed in Spain for a Spanish employer, Spain will generally have taxing rights. Belgium may apply exemption with progression, meaning the income is declared but not taxed again as ordinary Belgian salary.
Can I rent out one room and still keep the Brussels abatement?
Possibly, yes. Renting out one room does not automatically cancel the abatement if you still genuinely occupy the property as your principal residence. The risk increases if the property is no longer your real main home.
How is a furnished room rental taxed in Belgium?
For the immovable part, private residential rental is generally taxed based on cadastral income, not actual rent. If furnished, 40% of the rent is presumed to relate to furniture unless the lease provides another split, with a 50% expense deduction and generally 30% tax on the net movable income.
Should I deregister from Belgium if I live mainly in Spain?
Not without checking the consequences first. Deregistration may be the correct residence step if you have truly moved, but it can also be strong evidence that the Brussels principal residence condition has ended, which may affect the abatement.
Sources
Brussels Region — Abatement on registration duties — https://be.brussels/fr/impots-financement/impots-et-taxes/fiscalite-immobiliere/droits-denregistrement/abattement-sur-les-droits-de-vente
Degroof Petercam — Brussels registration duty reform and former abatement regime — https://www.degroofpetercam.com/fr-be/blog/reforme-droits-d-enregistrement-bruxelles
SPF Finances — Leaving Belgium and Belgian tax residence criteria — https://fin.belgium.be/fr/particuliers/international/quitter-belgique/declaration-impot
SPF Finances — Foreign income to be declared by Belgian residents — https://fin.belgium.be/fr/particuliers/international/revenus-comptes-etrangers/revenus
Belgian Embassy in Spain — Belgium-Spain double tax treaty — https://spain.diplomatie.belgium.be/fr/services-consulaires/autres-services-consulaires/convention-espagne-et-belgique-pour-eviter-double-imposition
Agencia Tributaria — Individual tax residence in Spain — https://sede.agenciatributaria.gob.es/Sede/en_gb/no-residentes/residencia-personas-fisicas-juridicas/persona-fisica-residente-espana.html
SPF Finances — Belgian tax return 2026 deadlines — https://fin.belgium.be/fr/particuliers/declaration-impot/rentrer-declaration/declaration-impot
SPF Finances — Non-resident tax return in Belgium — https://fin.belgium.be/fr/particuliers/declaration-impot/rentrer-declaration/non-residents/declaration
SPF Finances — Rental to a private individual and furnished rental rules — https://fin.belgium.be/fr/particuliers/habitation/louer-donner-location/revenus-locatifs/particulier
Brussels Region — Registration of residential leases — https://be.brussels/fr/logement/location/bail-dhabitation/enregistrement-bail-dhabitation
Agencia Tributaria — Spanish residents with foreign income — https://sede.agenciatributaria.gob.es/Sede/en_gb/ciudadanos-familias-personas-discapacidad/residentes-rentas-procedentes-extranjero/obtencion-rentas-extranjeras-reglas-generales.html
Agencia Tributaria — 2025 Spanish income tax campaign dates — https://sede.agenciatributaria.gob.es/Sede/ayuda/contenidos-lectura-facil/calendario-contribuyente-2026-simplificado-personas-fisicas/fechas-campana-renta-patrimonio.html
Agencia Tributaria — Modelo 720 reporting threshold — https://sede.agenciatributaria.gob.es/Sede/en_gb/todas-gestiones/impuestos-tasas/declaraciones-informativas/modelo-720-decla_____sobre-bienes-derechos-extranjero_/preguntas-frecuentes/forma-calcular-limite-que-obliga-declarar.html
Agencia Tributaria — Modelo 720 filing period — https://sede.agenciatributaria.gob.es/Sede/todas-gestiones/impuestos-tasas/declaraciones-informativas/modelo-720-decla_____sobre-bienes-derechos-extranjero_/plazos-presentacion.html
Agencia Tributaria — Form 149 special regime deadline — https://sede.agenciatributaria.gob.es/Sede/en_gb/ayuda/calendario-contribuyente/calendario-contribuyente-2026/informacion-sobre-presentacion-modelos-no-periodicos/impuesto-sobre-renta-personas-fisicas.html
This article sets out a general framework and is not a personalised tax opinion. Tax rules and filing deadlines can change from year to year, and the correct treatment depends on the exact residence, income, property and treaty facts.
Need tax advice tailored to your situation?
Have a similar situation? Befiscal has already handled files like this one. To get a written tax analysis tailored to your own figures and situation, click the “Ask your question” chat button on the right of this page: our assistant takes over, gathers the information needed and guides you through to your personalised written analysis.