Thematic investment deduction attestation: Energy-saving, renewable energy investment

On 18 May 2026, the Flemish Energy and Climate Agency (VEKA) published (Dutch) the attestation process for the thematic investment deduction applicable to investments in energy-saving and renewable energy included in the energy list.

The thematic investment deduction is a Belgian tax incentive with deduction rates of up to 40%, generating a saving of up to 10% on eligible investments (based on the standard corporate income tax rate of 25%).

Online application available for attestation in Flanders

Online attestation is currently available for investments made in Flanders and mentioned in the energy list (annex II, Code of Income Taxes 1992):

• Group 1: Limiting energy losses;

• Group 2: Recovery of energy and energy sharing;

• Group 3: Adjustment of equipment, installations, and industrial processes;

• Group 4: Flexibility—Temporary storage of electrical and thermal energy; and

• Group 5: Renewable energy.

Important reminder on funding combinations

The tax law changes of 18 December 2025 (Dutch | French) allow the thematic investment deduction on assets that receive regional funding. However, there is an important caveat: investments financed through Flemish ecology programmes—such as VLAIO's Energy Premium+, Strategic Ecology Support, or GREEN support—cannot be combined with any other governmental support, including the thematic investment deduction.

This restriction is based on the Flemish government’s decision (Dutch) of 19 April 2024 on ecological investment support.

Companies should carefully review their funding sources to ensure compliance.

Application in corporate tax return

Although the VEKA portal is operational, attestations will only be issued after the governmental cooperation agreement is signed, the timing of which remains uncertain. Companies intending to claim the deduction for investments made in 2025 are recommended to build a detailed defence file (including detailing the calculation of the internal rate of return and payback time, and energy study (where applicable)) to support applications in the corporate tax return for the financial year 2025.

What about investments in Brussels and Wallonia?

At this stage, online application is only available for relevant investments realised in Flanders.

Leefmilieu Brussel/Environnement Brussels is expected to be responsible for the certificates; however, no application process has yet been published for the thematic investment deduction.

SPW Wallonia mentions on its website (French) that applications for investments in 2025 and 2026 are suspended until the cooperation agreement is signed. Companies may submit an intention to apply, but this will not be considered a formal application.