Belgium's Capital Gains tax: 130 pages later, here are five points that really matter

Back in the office... and straight into one of the most anticipated Belgian tax developments of the year.

The Belgian tax authorities have finally published their 130 pages Circular on the new Capital Gains Tax applicable as from 1 January 2026.

Rather than summarising 130 pages, here are the five practical takeaways that, in my view, will have the greatest impact on entrepreneurs, investors and advisers.

Private Equity structures receive welcome confort

The Circular confirms that founders reinvesting alongside a private equity fund should generally remain outside the 33% internal capital gains regime, provided they do not control the acquisition vehicle alone (or together with their close family).

A major clarification for Belgian M&A transactions.

Family businesses gain greater legal certainty

Family successions and several common family holding structures are expressly addressed.

This is reassuring for many family-owned businesses, although careful structuring remains essential throughout the life of the structure—not only on day one.​

31 december 2025 has become the critical valuation date

For many taxpayers, future taxation will largely depend on one simple question:

Can you substantiate the value of your financial assets on 31 December 2025?

Documentation is now just as important as the tax rules themselves.​​

International mobility deserves careful planning

The Circular provides further guidance on the exit tax.

One particularly noteworthy point: automatic payment deferral is not available for several important jurisdictions, including the United States and the United Kingdom .

Cross-border moves should therefore be anticipated well in advance.​

The Circular provides certainty but not complete certainty

Several practical questions have now been clarified.

Others remain open.

Additional guidance—particularly regarding the withholding tax mechanism—is still expected.

My main Takeaway

This Circular will influence how Belgian entrepreneurs, investors and family businesses approach exits, reorganisations, succession planning and international mobility for years to come.

In many situations, the biggest risk will no longer be applying the wrong tax rate...

...but failing to document the right facts at the right time ​