The Belgian Tax Authorities have announced an extension to the filing deadline for both the Domestic Minimum Top-up Tax (DMTT) return and the IIR top-up tax return through administrative tolerance ( NL / FR ). The first filing deadline for these returns is now extended to 30 September 2026. For the DMTT return, this marks the second extension of the original first filing deadline of 30 November 2025 (see: Extended Belgian DMTT-return filing deadline ). This announcement follows the recent developments, including the launch of the public consultation on the draft IIR top-up tax return template (see: Belgian draft IIR top-up tax return) and the publication of the draft DMTT return template (see: Belgian Draft Domestic Top-up Tax Return).
Legislative deadlines
Under the Belgian Law on minimum taxation, the deadline for filing the DMTT return is the last day of the 11th month following the end of the fiscal year. The deadline for filing the IIR top-up tax return is aligned with that of the GloBE Information return. Accordingly, the deadline is the last day of the 15th month following the closure of the fiscal year, but the first filing deadline is extended to the last day of the 18th month following the fiscal year that begins by the latest on 31 December 2024.
Extended deadlines
The administrative tolerance extends all DMTT and IIR top‑up tax return deadlines falling before 30 September 2026 to 30 September 2026.
More precisely, for the DMTT return, this deadline applies to fiscal years that begin on or after 31 December 2023 and end no earlier than 1 January 2024 and no later than 30 September 2025
For the IIR top‑up tax return, this deadline applies to fiscal years that:
- begin on or after 31 December 2023 and no later than 31 December 2024, and end no later than 28 February 2025; or
- begin on or after 1 January 2025 and end no later than 31 May 2025.
The Belgian Tax Authorities will issue further guidance and technical details regarding the filing process.
How can KPMG help you?
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.
