On June 25, 2026, the Supreme Court issued its ruling in the so-called “mass objection plus” proceedings regarding Box 3. The outcome is disappointing for many taxpayers: those who did not file an objection at the time will not receive a tax refund.
In this article, we explain exactly what was decided and what this means for you.
Background
In the well-known “Kerstar” ruling of December 24, 2021, the Supreme Court ruled that, as of 2017, the Box 3 tax is in violation of European law if tax is levied on a higher notional return than the actual return.
However, taxpayers who did not file an objection—or did not file it on time—are, in principle, not entitled to legal redress, i.e., a reduction in their tax assessment, as a result of the Kerstar ruling. This led to legal proceedings, in which the Supreme Court issued its ruling on June 25, 2026.
What has the Supreme Court decided?
The Supreme Court has ruled that:
- Those who did not file an objection (or did not file it on time) are not entitled to a reduction in their Box 3 tax assessments for the years 2017 through 2020.
- This applies if the assessment was already final and binding prior to the Kerstar ruling (that is, if a final assessment is dated November 11, 2021, or earlier, and no objection was filed against it in a timely manner).
- The Supreme Court sees no reason to reverse its earlier ruling from 2022, which also determined that taxpayers who did not file an objection (or did not file it on time) are not entitled to legal redress.
- According to the Supreme Court, there is no discrimination between those who filed objections and those who did not.
The rationale is legal. If a tax assessment is final and has been set too high, the Tax Authority is not required to revise it if the excess tax results from new case law (such as the Kerst ruling).
In our view, the Supreme Court does leave some room for eligibility for legal redress in cases of an occasional excessive burden, but we do not expect this to occur often in practice.
Rebuttal Rule Effective in 2021
The situation is different for subsequent years. For tax years starting in 2021, you do have the option to use the rebuttal rule. This allows you to demonstrate that your actual return is lower than the flat-rate return.
Key points to note:
- This can also be done retroactively by requesting an ex officio reduction (using the Actual Return Statement (OWR) form).
- The deadline for this is 5 years after the end of the calendar year. For the year 2021, the OWR form must therefore be submitted no later than December 31, 2026.
It is therefore wise to assess (or have assessed) in a timely manner whether your actual return was lower than the flat-rate return.
Objection OptionsFor the various years in which you are entitled to invoke the rebuttal rule, you may still file an objection within 6 weeks of the date of the final income tax assessment. Filing an objection is only worthwhile if your actual return is lower than the flat-rate return.
By filing an objection:
- You may still be entitled to reimbursement of expenses.
- It remains possible to optimize the allocation of Box 3 income between tax partners, even after a potential reduction in Box 3 income due to a lower actual return.
Filing an objection is separate from the option to use the rebuttal rule and report your actual return. By filing an objection, you gain additional rights.
Starting with the 2025 tax year, it will be possible to report the actual return directly on the income tax return. This will no longer need to be done retroactively.
In conclusion
The Supreme Court’s ruling applies solely to the years 2017 through 2020. At the same time, options do remain for the years starting in 2021 and beyond.
Would you like to have your situation assessed to determine whether filing an objection or a request for a reduction is advisable? Please contact us through your account manager, by phone at 040 – 2 504 504, or via the contact form below, so that we can work with you to explore the options available in your specific situation.