Declaring foreign real estate in Belgium: how to do it

Cadastral income for foreign real estate: how its determined and how to request it

Since 2021, the Belgian administration assigns a cadastral income to foreign real estate, comparable to Belgian property. That KI is not derived from the actual rent but from the theoretical annual net rental value in the reference year 1975. The calculation starts from the propertys current normal sales value and brings it back to 1975 via statutory correction factors, after which indexation and flat-rate increases are applied under Belgian rules.

• Built properties: KI via a correction factor on the market value, followed by indexation and a flat-rate adjustment according to the personal income tax rules.
• Unbuilt properties such as building land: specific reference methods, likewise brought back to 1975 and indexed.
• Rental to individuals for private use: in the Belgian return you use the KI as the starting point.
• Rental for professional use: the treatment differs; inform yourself about the impact on the exemption and the calculation basis in Belgium.

Apply digitally via MyMinfin or on paper. Report a new foreign property in good time after you have acquired it. After your notification you will receive the decision with the KI. If you do not agree with the assessment, you can lodge an objection within two months of notification.

Common situations

You were not the owner for the full year

In your return you only count the part of the year in which you were owner or usufructuary. The pro rata is based on the number of days. Example: you purchased on 1 July and were therefore owner for 184 days. You declare 184/366 of the annual KI for a leap year, or 184/365 in a normal year.

You share ownership with someone else

In co-ownership, each person declares their own share. If you are a 50 percent co-owner, you report 50 percent of the cadastral income in your return. Always state the right you exercise, for example bare ownership or usufruct, and the corresponding proportion. If this changes during the year, apply both share and period pro rata.

Country with treaty or without treaty

The existence of a double tax treaty determines whether Belgium can apply an exemption with progression. In broad terms:

Penalties and audits: what if you do not declare?

The administration increasingly receives data on foreign real estate through international exchange. Not declaring can lead to administrative fines per property, with the amount varying depending on the assigned KI. You can also risk late-payment interest or an assessment based on an estimate. Timely reporting and correctly including the KI in your return helps you avoid unnecessary sanctions.

Checklist: documents and supporting evidence

• Deed of purchase or notarial deed with the date and description of the property
• Your property right and share as stated in the deed or agreement
• Address, surface area and characteristics of the property, including year of construction and type
• Current market value or comparable references if requested for the KI calculation
• Lease agreements and nature of the tenant  private or professional
• Evidence of foreign levies such as local property tax or income tax
• Belgian KI decision and any correspondence for your file

FAQ: declaring foreign real estate in Belgium

How is foreign real estate taxed?

With a double tax treaty, the immovable income is usually taxed abroad. Belgium then applies an exemption with progression: the income counts to determine your rate but is not taxed twice. Without a treaty, Belgium can tax the income itself according to Belgian rules, generally based on the cadastral income.

What is the penalty for not declaring a foreign home?

There are administrative fines that are imposed per property and can increase depending on the assigned cadastral income and the seriousness or repetition. Besides the fine, you also risk late-payment interest. Prevent this by reporting on time via MyMinfin and correctly including the KI in your return.

What should I report under code 1106 in the 2025 personal income tax return?

The code numbers in box III Immovable income differ by tax year and by situation. In practice you report the cadastral income of your foreign real estate in the correct section for foreign immovable income, with the code number provided in your current filing instructions. Always check the most recent guidance in your return or on MyMinfin.

How do you declare foreign income in Belgium?

Immovable income from abroad is reported in box III Immovable income, based on the Belgian cadastral income. Other foreign income such as movable or professional income belongs in their respective boxes. Consult the specific instructions and treaty application per source of income.

This information is general and does not replace individual tax advice. In complex situations, it is advisable to align your case with your accountant or tax adviser. Christies International Real Estate Belgium is happy to help with your real estate questions and international purchase or sale plans. Do you have a specific question? Contact us for personal advice.