The draft bill on the reform of personal income tax, submitted to Parliament on 14 January 2026, provides for the gradual abolition of the marital quotient mechanism. Once adopted, this measure will significantly affect the tax position of many single-income couples or couples with highly unbalanced incomes.

The marital quotient, which applies to married couples and legally cohabiting partners, currently allows up to 30% of the professional income of the higher-earning partner to be notionaly attributed to the other partner where the latter earns little or no professional income.
This attribution is, however, subject to a cap (€13,460 for assessment year 2026).
The draft bill provides for a gradual abolition, with differentiated rules depending on the taxpayers concerned:
The reform is driven by the intention to strengthen tax neutrality between different forms of cohabitation, as the marital quotient is not available to de facto cohabitants. It also reflects a broader shift towards a tax system that is less centred on the single-income household model. Finally, the legislator considers that the mechanism may act as a disincentive to labour market participation by the second partner.
In practice, this reform may result in a gradual increase in the tax burden for certain households, making it advisable to anticipate its impact in light of the household’s income structure.
As the bill has not yet been definitively adopted, amendments remain possible. We will, of course, keep you informed of further developments.
At Andersen in Belgium, we remain at your disposal to assess the concrete impact of these measures on your personal tax situation.
If you have any questions about this topic or require assistance in the context of a dispute with the tax authorities, please do not hesitate to contact the tax department at Andersen.
Sébastien Watelet (Tax Partner) & Océane Magotteaux (Associate)
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