Following the publication of the Royal Decree of 16 June 2026 in the Belgian Official Gazette on 25 June 2026, a temporary tolerance measure has been introduced for companies investing in eligible energy or environmental projects in Belgium. They can temporarily claim the enhanced thematic investment deduction for investments made or completed between 1 January 2025 and 31 December 2026, without yet having obtained the required attest (= the regional certificate required to claim the deduction).
Initially, the usual three-month deadline following the end of the financial year had been extended until 30 June 2026 for investments made in 2025. However, under this new administrative tolerance, the deadline for requesting the regional attest to be able to claim the enhanced thematic investment deduction has been extended until 31 December 2026.
Table of content
What is new?
Under this measure, taxpayers can provisionally claim the enhanced thematic investment deduction in their 2026 corporate income tax return, even if the required attest has not yet been issued. Note that the extended deadline does not guarantee entitlement to the deduction, which remains subject to the approval of the attest by the competent authorities.
To benefit from this tolerance, companies must be able to demonstrate a reasonable basis for believing that the investment qualifies, supported by documentation such as technical assessments, expert reports, invoices, quotations, or other relevant evidence. Where an attest application has already been submitted, proof of submission can serve as additional support.
Importantly, this is only temporary administrative relief. Taxpayers must still apply for and obtain the attest once the attestation process is fully operational. In the event of a tax audit, a positive attest will ultimately be required to secure the tax benefit.
Current Status by Region
- Flanders (VEKA) : the application process is available, but certificates will only be issued once the Cooperation Agreement between the relevant governments has been finalised and published. Applications are currently limited to investments included on the energy list, while environmental investments are expected to be added at a later stage.
- Wallonia : the regional authorities indicate that the scheme is still being implemented and that the application process will become available in due course.
- Brussels-Capital Region : requests for a tax certificate can be submitted either by post or by email to their email address.
For multi-year investment projects, taxpayers can apply for an investment certificate, even before the project starts. This certificate guarantees that the conditions in effect at the time of the application will remain in effect for the entire duration of the project, even in the event of a subsequent triennial review of the list of eligible investments. However, it does not automatically grant access to the deduction; an annual attest remains necessary to claim the tax benefit.
IRR and TVT requirements
To benefit from the enhanced thematic investment deduction for investments in energy efficiency and renewable energy, companies must demonstrate that the investment is sufficiently cost-effective.
- All companies must show a payback period (TVT) exceeding three years.
- Medium-sized and large companies must also demonstrate that the investment’s internal rate of return (IRR) does not exceed 13%.
How Ayming can help
The current transitional framework creates an opportunity but also requires careful preparation. The best way to anticipate is to prepare the strongest possible case and closely monitor legislative developments, as well as ensuring full compliance with the tax authorities’ guidance. Ayming supports companies throughout the process by:
- Assessing investment eligibility
- Preparing and submitting attest applications
- Advising on the supporting documentation required
- Monitoring regulatory developments to adapt your approach
With our expertise in innovation funding and tax incentives, Ayming is your partner to maximise your chances of securing the enhanced thematic investment deduction.
Want to Go Further? Talk to Our Experts
