What does the capital gains tax reform mean for financial institutions?

From political footnote to full-fledged reform

What started as a brief seven-line mention in a political agreement has expanded into a comprehensive 76-page draft law, becoming one of the most debated issues in the formation of Belgium’s federal government. The new capital gains tax reform is now approaching its final stages.

The practical impact on Financial Institutions

While the draft includes some quirky references, such as buying pizza with Bitcoin, and a few technical inconsistencies, the real impact lies in what this means for the financial sector.

At its core, the reform introduces a 10% withholding tax on certain gains realised by Belgian residents on a specified range of financial instruments. On the surface, this seems straightforward, but the practical implementation promises to be more complex.

Financial institutions, especially banks and investment platforms, will be required to automatically withhold this tax by default on qualifying transactions. At the same time, an opt-out mechanism will allow individuals to choose not to have the tax withheld at source and instead declare the gains themselves. However, the specifics of this opt-out process remain unclear.

Tight deadlines, open questions

In addition to the opt-out details, there are still open questions about what exactly needs to be reported to tax authorities, and how withheld taxes must be transferred to the government.

With a hard deadline set for 1 January 2026, financial institutions face a classic delivery dilemma. A regulatory obligation introduced late in the planning cycle, with no room for delay, and added to an already packed transformation agenda.

And with the government signalling little willingness to postpone or phase the rollout, many transformation leaders are quietly grappling with the difficult question,

“what happens if the IT systems aren’t ready?”

Preparing your organisation for the capital gains tax reform

To avoid scrambling under pressure, financial institutions need to start with a thorough impact assessment. That means evaluating how this new tax will affect their operating model end-to-end.

At an operational level, financial institutions will need to install processes to track capital gains at the client level and calculate the tax correctly, taking into account exemptions, progressive rates, and other relevant criteria.

In parallel, IT systems must be updated or in some cases completely overhauled to support accurate calculation, application, and reporting of the withholding tax.

Institutions should also prepare for increased reporting obligations to the tax authorities. Accuracy, traceability, and auditability will be essential.

On the commercial side, clients will expect clear, proactive communication. Some may seek more tax advice, increase their trading activity, or even move assets abroad to reduce exposure.

Now is also the right moment to review how you stay on top of regulatory change. Tools like Ruler can help monitor updates in real time, assess their impact, and support your organisation in staying compliant without the scramble.

More than just a compliance challenge

Could the reality become a “Wizard of Oz” scenario, where customers experience seamless, compliant interactions, while behind the scenes, operations teams manually manage processes with spreadsheets and late-night workarounds?

This seems to be a strong reminder that transformation is not just about delivering software, it’s also about building institutional agility.

As the regulatory dust begins to settle, one thing is clear. This reform is more than just a compliance challenge it might also be an opportunity to differentiate. Whether customers opt in to the default 10% withholding or choose to declare gains themselves, they will need clear, timely, and accessible information to make informed decisions.

Getting this right might not grab headlines, but in a complex tax environment, being the institution that communicates transparently, supports proactively, and empowers customers to feel in control is the quiet advantage that builds lasting trust.

We’ll be publishing a more in-depth article soon, offering concrete guidance on how to prepare for the upcoming changes. In the meantime, if you have any questions or would like to explore the implications for your organisation, feel free to get in touch.