The Capital Gains Tax: more details.

Opt-In? Opt-out?

What does this actually mean & when does it go into effect?

Belgian Financial Institutions will -from the tenth day after publication of the law- have to withhold a withholding tax (10%) on all capital gains realized since 1/1/2026, unless you request them not to do so. This is the "OPT-OUT."

As long as the law has not been published, those same Financial institution may not automatically do so unless you instruct them to do so. This is the "OPT-IN".

Following your choice of Opt-in or Opt-out:

If you choose Opt-in

(automatic deduction by your financial institution), you do not have to do anything further, nor are you required to declare this income in your personal income tax. After all, the tax due has already been withheld and is "freeing". This ensures a degree of discretion.

If, however, you wish to take advantage of the €10,000 exemption and/or bring in any capital losses, you will still have to declare the capital gains involved in your tax return as well, along with the capital losses realized in the same year.

If you choose Opt-out

(no automatic deduction), the financial institution will report the details and information of your realized capital gains to the Belgian tax authorities. You must declare all realized capital gains and losses yourself in your tax return. Your financial institution will provide you with an annual statement for this purpose.

If you do not make a choice

your financial institution will in principle not withhold any withholding tax until publication of the law. For this period you will then have to file your own tax return at a later date. As of the publication of the law, the bank will withhold a withholding tax.

Important:

Currently, financial institutions are offering the opportunity to apply the withholding tax retroactively for the period between January 1, 2026 and the publication of the law. This way, they can guarantee your right to discretion and you can still wait for the publication of the law before making your choice.

Would you like to know more about the above matter? Do you have any other questions related to your assets in the broadest sense? Feel free to contact us for a no obligation consultation!