With the new Belgian capital gains tax on financial assets starting in 2026, a lot of the discussion focuses on what is taxed — but less on how this will actually work with your broker. That part matters just as much in practice.

Here’s a short breakdown based on current guidance:

1️⃣ The basics - Capital gains on financial assets will be taxed at 10% - There is a €10,000 annual exemption per person - Only gains realised from 1 Jan 2026 onwards are taxable - Assets are “reset” using their value on 31/12/2025 as the cost basis

2️⃣ Belgian brokers vs foreign brokers - Belgian brokers are expected to withhold the 10% tax automatically by default -- You’ll likely be able to opt out and declare gains yourself -- The broker does not apply the €10k exemption, so withholding can be higher than your final tax

  • Foreign brokers (DEGIRO, IBKR, Trade Republic, etc.) -- No withholding -- You must calculate gains yourself using the 31/12/2025 valuation and declare them in your tax return

3️⃣ Why this matters - Automatic withholding can mean temporary overpayment, with refunds only after filing your tax return - Self-declaring gives more control, especially if you: -- stay under the €10k exemption -- realise losses -- use multiple brokers

I wrote a more detailed, broker-by-broker guide (including opt-out timing and practical examples) here for anyone who wants the full picture: 🔗 https://tob.tax/en/brokers/cgt-guide

Disclosure: I’m one of the author of the linked guide. Sharing it because this question keeps coming up and I couldn’t find a clear overview focused on how brokers will handle this in practice.

Curious how others are planning to handle this — stick with withholding, opt out, or move everything to a foreign broker?

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  • Stupid question. If you stay under the 10k exemption, do you still need to declare anything?

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    Absolutely, the exemption doesn't mean you don't have to declare it (like the exemption on the first xxx euros on dividends - Forgot the amount), it must still be tracked by the fisc

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    So you have to declare everything that happened on your broker account now, even if you never pull any money out of the broker account during that particular fiscal year?

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    Only when you sell.

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    Yes:

    - opt-in: to retrieve back the exempt amount;

    - opt-out: to declare your profits (-losses)

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  • Great stuff! Nitpicking but this bullet under Foreign brokers should also be listed under Belgian broker with opt-out: You have losses to offset or expect to stay under the €10k exemption

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  • Great write up an website. Thanks OP.
    Question - Do I still need to report "unrealized" capital gains if the value of my portfolio grows but I never sold anything in 2026 ?

    parent

    no. it's about realized gains.

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  • I find the exemption rather difficult.

    So the first year i get 10K, let's say I use 500 €, I have 9500 € left that I move over the next year + get an additional 1K resulting in 10.500 € to be used. Let's say I use 200 €, then next year I have 11300 €.

    However they are also talking about indexing the amounts? How is that gonna work, are they just gonna say: this year the index is 106.13 with 31/12/2025 being 100?

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    The carry-over works differently: you can carry over a maximum of €1.000 to the next year, and this for max. 5 years in a row. I.e. in your example you don't carry over €9.500 but in the next year get €10.000 + €1.000 = €11.000 exemption.

    I would imagine they'll indeed index the €10.000 yearly exemption using a simple index, resulting each year in a small increase of that exemption amount.

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    I read in De Tijd that the carry-over works differently. You can only enjoy the extra 1000€ when you did not realise any gains the year before. So I interpreted it as: If you don't sell anything during the whole year, the following year you will have 11k€. From the second you sell and realise 1€ in capital gains, the next year you will have 10k€ again.

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    I think you're right which I find counter-intuitive, as you lose the entire €1000 carry-over as soon as you realized any gains at all. But looking deeper at the wording, I'm coming to the same interpretation as you.

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  • It is also important to mention that, for those who opt-out, Belgian brokers will (likely) provide a simple report where your gains are already computed. Hence, the only 'complicated' part for the investor will be to collect the reports from different brokers and integrate them in the tax declaration.

    parent

    .... Belgian "full service" brokers .....

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    Hopefully. And if you want to use the historical value rather than the end of 2025 valuation, you'll likely have to do that yourself. It's going to be an interesting exercise... and who will ever check all those manual aggregations?

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    I suppose the bank can also simply provide an 'pre-2026 average purchase price' for stocks sold for a loss. On the check part, I agree it will be a complex exercise.

    You can check this article, that also describes the FIFO concept for stock purchases after 01/01/2026:

    https://curvo.eu/article/belgium-capital-gains-tax

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    why "average" ?

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  • Question about the "Assets are “reset” using their value on 31/12/2025 as the cost basis" point, figures are just for the sake of clarity: (and also let's assume I'll have > €10k gains in 2026 for simplicity)

    If I bought 1000 stocks at €100 last year, then there was a crash and their value on 31/12/2025 dropped to €10, then in 2026 I decide to stop the bleeding and sell at €15, does that mean that it would be considered as €5k worth of capital gains for this operation?

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    The law still needs to pass, so it's all conjecture at this point.

    It's been previously reported on, however, that investors will have a choice between the value when you bought versus the value on 01.01.2026.

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    Can you elaborate a bit on the 'law still needs to pass' part? Thanks :)

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    The bill is still moving through the legislative process. There still needs to be a vote in the House of Representatives and be published in the Belgisch Staatsblad afterwards (if it gets through the House).

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    OK clear, thank you.

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  • i'll opt-out for sure. and report 9,999 at the end of the year.

    good luck enforcing this ridiculous tax code.

    i have three different brokers. bolero/keytrade/ibkr.

    i'm not gonna make my already complex life more complicated by playing these games.

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  • How do you guys do the 31/12/2025 valuation? Do you take a screenshot? doe the brokers provide a document? can i still find my valuation or am i too late? i'm with de giro, lynx and saxo

    can someone clearify the opt-out option?

    many thanks!

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    MEdirect took a snapshot of the balance at 31/12/25

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    I asked Gemini to give me the EUR value of each stock I own at the end of trading day on December 31st 2025.

    I doublechecked the prices and everything is correct. Luckily, I don't have stocks that were lower in value on the 31st of January than when I bought them.

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    For Degiro, there is a snapshot of your portfolio at 31/12/2025 in your documents (mine was called "Relevé d'Instruments financiers et de fonds Q4 2025"). I assume this will be the basis to be used for the calculation of the CGT.

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    Thanks! Totally forgot to take my own screenshot on the 31st...

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  • I have a dumb question but why can't Belgian brokers automatically deduce if you are above the 10k tax exemption and start taking the profits from that point? Am I missing something?

    parent

    Because broker A doesn't know what you're trading with brokers B, C and D?

    parent root

    Because many investors use more than 1 broker

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    Always the right answer !

    That's the same for interests above 1000€ on savings. They withhold in any case and government just hope you forget to declare.

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    For the savings tax free amount the law is different; each account applies the tax free amount.

    Many savers "forget" to declare the needed amounts and hence become tax frauds.

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  • Great content thank you.

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