Taxation in Belgium: Monthly Withholding taxes

In Belgium, employers have the obligation to withhold taxes at source, from your monthly payroll.

Monthly withholding taxes are however not a final tax, they are only an advance/pre-financing on the final taxes that will be due through annual tax return.

Taxation in Belgium: Annual Tax return

Belgian resident taxpayers have the obligation to file an annual tax return to report their worldwide income (this also includes professional, movable, immovable or various income generated abroad). Married taxpayers and legal co-habitants must file a joint tax return.

The "income year" corresponds to the calendar year, from 1st of January till 31th of December.

The "tax year" corresponds to the following year, when the tax return must be filed.

The annual tax return filing due date is usually set at 30th June (paper filing) or 15th July (Tax-on-Web filing) of the year following the income year.

Example : If you move to Belgium with your family on the 1st of August 2025, you will have to file a Belgian annual tax return by the 15th of July 2026, to report your worldwide income earned during the period August - December 2025.

When you tax return has been processed by Belgian tax authorities, you will receive a tax assessment (end of June 2027 at the latest for income year 2025). Once you receive your tax  calculation, you have 2 months to either pay extra due taxes or receive your tax reimbursement.      

Important note : In case you are moving out of Belgium in the course of the income year, you will have to file a "special" tax return to close your tax situation in Belgium. This special tax return does not follow the usual filing due date and must be filed anticipatively. More details can be found in the Leavers website.

Key Belgian tax documents

In Belgium, there is a form for everything. The key to eternal bliss is knowing which one to use!  Every month, you will receive a payslip issued by our outsourced payroll secretariat that will look like this: sample payslip

At the end of the year, a summary covering the income year is produced by SD Worx to help you with your Belgian tax filing.  This summary is called form 281.10. You will notice that a code appears next to each figure, which is in fact the tax code to be used in your filing.  As this is a tax document, the taxable income appearing under code 250 is equal to your annual gross salary, minus your 13.07% personal social security charges. Therefore, this is not your gross salary,  so this document should not be used when completing your US tax filing (US form 1046). Here is a sample of this form: sample 281.10 page 1       sample 281.10 page 2

Additionally,  a detailed breakdown of your compensation package month by month called a "compte individuel" is available for those of you who need this information for legal purposes. Although this document only exists in French, you can find a translation of its key terms here. Here is a sample of this form:  sample compte individuel page 1   sample compte individuel page2 

Tax Assistance on campus

Belgium's tax system is complicated, which is why ISB will help you to be compliant in Belgium.  There is a Belgian tax Assistance Week be conducted every year in June for all newcomers and employees being present in Belgium since less than 5 years. 

English-speaking tax consultants will be present in June 2025 on ISB campus and will provide assistance for the completion and filing of the Belgian tax return (individual scheduled meetings). The cost of this service is covered by ISB. Filing obligations in your country of origin,  if any, remain your responsibility.