Belgium: our calculator now applies the communal surcharge to the tax after the tax-free allowance

What changed

This note records a correction to our calculator, not a change in the law. In Belgium, every municipality levies a surcharge on personal income tax, at a rate of 0% to 9% depending on the municipality; our calculator uses a representative 7%. Article 466 of the Income Tax Code 1992 computes this surcharge “on the total tax”, that is, on the tax that remains after the reduction for the tax-free allowance (quotité exemptée d’impôt).

Until 18 October 2026, our calculator applied the 7% to the tax computed before that reduction. The page described the gap as a slight overstatement; it was more than that. For a single person without children, the communal surcharge counted 7% too much on the tax attributable to the EUR 11,550 tax-free allowance, that is EUR 202.125 a year at every salary where the allowance is fully used. Below that, an employee whose tax after the allowance was nil was still charged a communal surcharge: EUR 183.75 at EUR 15,000 of annual gross. The allowance rises with dependent children, and each spouse has their own when the marital quotient applies, so the gap grows accordingly. At EUR 60,000 gross it reaches EUR 309.15 for a single person with two children, EUR 404.25 for a married couple where only one spouse has professional income, and EUR 511.28 for the same couple with two children.

The order of computation matters as much as the base. Article 5/3 of the special law of 16 January 1989 on the financing of the Communities and Regions sets the sequence: the total tax, the sum of the federal and the regional tax, is first reduced by the refundable tax credits, then increased by the communal surcharge. The fiscal work bonus and the tax credit for dependent children therefore do not reduce the base of the communal surcharge. When they exceed the tax, article 304 of the same Code imputes the excess on the communal surcharge before refunding the balance, which, for net pay, amounts to deducting both from the total. Our calculator has followed this order since 18 October 2026, and its tax table now shows each step on its own row, the fiscal work bonus included.

Effective date

The sequence of article 5/3 of the special law, inserted by a law of 6 January 2014, has been in force since 1 January 2014. The programme law of 18 July 2025 only amended the second paragraph of article 466, which removes from the base the tax on certain investment income, with no effect on a salary. The law of 15 July 2026 reforming personal income tax adds to article 466 a correction factor on the base, set by the King to account for the fall in total tax that the reform brings; the factor applies only from assessment year 2029, and the 2026 income our calculator estimates is not affected. The correction has been live on the Belgium page of the calculator since 18 October 2026, in both languages.

Worked example

Figures produced by our net salary calculator, single person without children, white-collar employee (contributions on 100% of gross), representative communal rate of 7%, final tax for income year 2026, before and after the correction of 18 October 2026. Social contributions and the work bonus are unchanged.

The difference is 7% of the tax attributable to the tax-free allowance, that is 7% of EUR 2,887.50 = EUR 202.125 a year once the allowance is fully used; rounded to the cent, it shows as 202.12 or 202.13 depending on the row. At EUR 15,000 gross, the tax after the allowance is nil and the communal surcharge now is too. At that level, the work bonus cancels the personal contributions and its fiscal part, which exceeds the tax, is refunded up to EUR 784.42: this is why the annual net exceeds the gross.