Executive summary

On 3 April 2026, the Belgian tax authorities announced a further extension of the filing deadlines for the Qualified Domestic Minimum Top-up Tax (QDMTT) return and the Income Inclusion Rule (IIR) return (link: Pillar 2 - Uitstel voor de indiening van de aangiften inzake de binnenlandse bijheffing en de IIR-bijheffing | FOD Financiën).

All Belgian QDMTT and IIR returns for which the statutory filing deadline would otherwise fall before 30 September 2026 are now deferred to 30 September 2026.

QDMTT return — filing deadline extended

Under domestic law, QDMTT returns are in principle due by the last day of the 11th month following the end of the fiscal year. Last year, the Belgian tax authorities granted a filing extension for the first FY2024 filings till 30 June 2026 (see EY Global Tax Alert, Belgian QDMTT return deadline extended till 30 June 2026, dated 17 November 2025).

The Belgian tax authorities have now further extended the previous extension for QDMTT return filings until 30 September 2026. This extended deadline applies to QDMTT returns relating to fiscal years that start on or after 31 December 2023, and end no earlier than 1 January 2024 and no later than 30 September 2025.

IIR return — filing deadline extended

Domestic law provides that the filing deadline for the IIR return is the last day of the 18th month following the end of the fiscal year that starts no later than 31 December 2024, or the last day of the 15th month following the end of the fiscal year that starts no earlier than 1 January 2025.

For IIR returns relating to fiscal years that:

• Start on or after 31 December 2023 and no later than 31 December 2024, and end no later than 28 February 2025, the filing deadline is extended until 30 September 2026
• Start no earlier than 1 January 2025 and end no later than 31 May 2025, the filing deadline is extended until 30 September 2026

Implications and next steps

The Belgian tax authorities confirm in their press release that practical filing instructions and technical documentation (including return formats and submission procedures) will be published at a later stage. As of today, the Belgian Pillar Two filing platform is not yet open, and the final forms and technical instructions have not been published.

As a reminder, a draft QDMTT return template and a draft IIR return template, with draft accompanying guidance, was recently issued (see EY Global Tax Alert, Belgium publishes (updated) draft Pillar Two returns and guidelines, dated 31 March 2026).

The press release is silent as to the filing of the Global Anti-Base Erosion (GloBE) Information Return (GIR) and/or the GIR notification, both of which have a first filing deadline for most in-scope groups on 30 June 2026.

Although a further extension has been granted for the QDMTT return and IIR return, in-scope taxpayers should continue to prepare, finalize and file (once practically feasible) the (local) Pillar Two returns based on the draft templates available, as the new filing deadlines will coincide with the annual corporate income tax return and local transfer pricing filing deadlines.

Affected groups should consider engaging tax advisors for assistance with compliance obligations and last-mile support.