The law on capital gains tax will not yet have been passed at the start of 2026. You can read below the various ways you can choose to pay the tax.
1. How do you pay the tax?
Once the law enters into force, you have two options:
- Option 1: Declare everything yourself (opt-out)
- You opt for KBC Brussels not to deduct any capital gains tax
- We report your choice to the tax authorities and provide you and the tax authorities with a statement detailing your realised capital gains
- You are personally responsible for declaring these amounts in your tax return
How do you make this choice?
From the end of January 2026, you can easily arrange this in KBC Brussels Mobile, KBC Brussels Touch or in your KBC Brussels branch. You will receive additional information in this regard at that time.
- Option 2: Automatic deduction (withholding tax)
- If you don’t opt out, KBC Brussels will automatically deduct 10% capital gains tax when you realise a gain on selling an investment
- We will transfer that amount anonymously to the tax authorities
- If you decide to use the exemption, you can claim back the amount paid on your tax return (we'll provide you with a statement for this purpose)
How do you make this choice?
You don't have to do anything for this option.
Example
You sell shares in June 2026 and realise a capital gain of 9 000 euros. Your financial institution will deduct capital gains tax of 900 euros on this transaction and will itself forward the money (anonymously) to the tax authorities. Since you can make use of the exemption of 10 000 euros, you can declare this capital gain on your tax return for your income year 2026/assessment year 2027 in order to recover the tax paid of 900 euros.
Tax cannot be deducted at source for certain financial products (such as capital gains on crypto-assets, foreign currency and gold). For these products, you are responsible for declaring any capital gains on your own personal income tax return.
For securities that you hold outside Belgium, you will also have to declare any realised capital gains on your personal income tax return.
For non-profit organisation and foundations, the system of deducting the tax at source does not apply; instead, payment of the capital gains tax is arranged directly through the legal entities withholding tax return.
If you are co-holder of a joint account
Every account-holder has to make the same choice (declare everything yourself or opt for automatic deduction).
2. How do you pay before the law enters into force?
The tax applies as from 1 January 2026, but the law will not be published until later.
- If you decide to opt out and therefore don’t have the tax deducted automatically, it is your responsibility to declare all the capital gains realised in 2026 in your tax return.
- If you’ve opted for the tax to be deducted automatically, KBC will start KBC Brusselswithholding it as soon as the law enters into force.
The government is still working on a solution for capital gains realised during the transition period.