Belgian draft IIR top-up tax return

The Belgian tax authorities have published the draft IIR top-up tax return and explanatory notes for public consultation (see: NL / FR ). Stakeholder feedback is requested by 3 April 2026 by e-mail to pillar2@minfin.fed.be.

Under the Belgian law on minimum taxation, an IIR top-up tax return must be submitted to declare the IIR top-up tax. Each taxpayer subject to the IIR top-up tax must file its own tax return. Consequently, multiple IIR top-up tax returns may be filed for a single group. The IIR top-up tax return is a formal tax return and triggers an assessment notice by the Belgian tax authorities.

The filing deadline for the IIR top-up tax return is aligned with that of the information return (the Belgian equivalent of the GIR/TIR). The deadline is the last day of the 15th month following the fiscal year, but the first filing deadline is extended to the last day of the 18th month following the fiscal year that begins at the latest on 31 December 2024. Where the fiscal year coincides with the calendar year, this means that for fiscal year 2024 the first filing deadline is 30 June 2026.

KPMG can assist you with all compliance aspects of the global minimum tax in Belgium and globally, including registration, calculation of tax liabilities, and filing of the required returns. In addition, we can help you identify the relevant data points, collect the necessary data, and perform the calculations for all top-up taxes.

If you have any questions regarding the applicable rules and their implications for your business, or if you require assistance with the Belgian minimum tax, please do not hesitate to contact your trusted KPMG advisor or reach out to us directly.