The declaration obligation
Yes, every owner of real estate in Belgium must declare their property income, even for unlet properties. For a private let or unlet property, declare the non-indexed CI in Part III. For a professional let or let to a company, declare the actual gross rent. Non-compliance carries surcharges of 10 to 200%.
This obligation applies regardless of whether the property generates rental income. An owner-occupied property, a vacant property, or a property used for free all require CI declaration.
What to declare in practice
| Situation | What to declare | Where |
|---|---|---|
| Owner-occupied | Non-indexed CI | Part III, box 1100/2100 |
| Let to a private individual | Non-indexed CI | Part III, box 1106/2106 |
| Let to a company / professional use | Actual gross rent | Part III, box 1109/2109 |
| Vacant property | Non-indexed CI | Part III, box 1100/2100 |
| Foreign property | Rental value or actual rent | Part III |
You own two apartments: one is your primary residence (CI EUR 800, exempt from taxation), the other is let to a private individual (CI EUR 1,100). You declare EUR 1,100 in Part III. The tax authorities handle the indexation and 40% increase automatically.
Penalties for non-compliance
Failure to declare rental income can result in serious consequences:
- First offence: tax surcharge of 10% on the evaded tax
- Repeated offence: surcharge of 20 to 50%
- Deliberate fraud: surcharge of 50 to 200% + potential criminal prosecution
- Extended statute of limitations: 7 years instead of 3 in case of fraud
The tax authorities cross-reference data from lease registrations, cadastral records and banking information. An unregistered lease or undeclared property is increasingly likely to be detected.
Use the Tax-on-web portal to verify which properties are already pre-filled in your return. Missing properties should be added manually.
Regional specifics
Brussels-Capital Region
The declaration obligation is federal and applies uniformly. Brussels Fiscalite manages property tax separately but shares data with the FPS Finance.
Walloon Region
Same federal rules. The SPW Fiscalite cooperates with the FPS Finance for data matching between property tax and income tax returns.
Flemish Region
Same federal rules. VLABEL manages property tax and shares data with the federal tax authorities for cross-checking purposes.
Articles 7 to 13 CIR 92 (property income declaration), Articles 444 to 445 CIR 92 (tax surcharges) — Texts on Justel