These filing obligations arise from the Act of 19 December 2023 introducing a minimum tax for multinational enterprise groups and large-scale domestic groups.
The returns that qualify for this new extension are the following:
Returns relating to the domestic top-up tax (QDMTT) with respect to financial years that:
- start on 31 December 2023 or later, and
- end at the earliest on 1 January 2024 and at the latest on 30 September 2025.
Returns relating to the IIR top-up tax with respect to financial years that:
- start at the earliest on 1 January 2025 and end at the latest on 31 May 2025, or
- start from 31 December 2023 and at the latest on 31 December 2024, and end at the latest on 28 February 2025.
One single deadline: 30 September 2026
For all returns relating to the domestic top-up tax and the IIR top-up tax for which the statutory filing deadline falls before 30 September 2026, the filing deadline is uniformly extended until 30 September 2026. This new extension partially follows on from the previous extension announced on 17 November 2025, according to which the filing deadline had already been extended to 30 June 2026.
The tax authorities further indicated that the practical guidelines and technical documentation regarding the filing procedure will be published at a later stage.
How Grant Thornton can support you
Although this additional extension provides more time, the Belgian Pillar Two obligations remain particularly complex.
We strongly encourage you to review your current compliance process and determine internal timelines to meet the revised deadline. With our expertise, Grant Thornton can assist with the preparation, review and/or filing of Belgian returns. The extended deadline makes this an ideal moment to clearly identify responsibilities for the various data points within your group and to start collecting the required information already, so that filing can take place smoothly and in a timely manner.
Please contact us to discuss how we can support you in complying with the Belgian Pillar Two filing requirements.
