Belgium's tax authority has opened its online filing system for 2025 income declarations, with standard electronic submissions due by 15 July 2026 and extended deadlines available until 16 October 2026 for taxpayers with self-employed or foreign professional income.
Belgium’s Federal Public Service (SPF) Finance has launched its Tax-on-web e-service on 28 April 2026, enabling taxpayers and tax professionals to file personal income tax returns for the 2026 assessment year covering 2025 income.
Taxpayers have different submission deadlines depending on their filing method. Those submitting paper returns must file by 30 June 2026, while electronic filers using Tax-on-web have until 15 July 2026 to complete their submissions.
However, certain taxpayers with specific income types—including self-employed income, foreign professional income, and other designated categories—may qualify for an automatic extension until 16 October 2026.
Tax professionals using Tax-on-web Mandataire can access their client lists, which display each client’s filing deadline. When clients qualify for the extended October deadline, representatives can indicate this directly in the system by checking the appropriate box and attaching supporting documentation as needed.
For clients who receive simplified declaration proposals but should qualify for the 16 October 2026 deadline, tax advisers must contact SPF Finance Services no later than 15 July 2026 to request the extension.
Taxpayers who discover errors or omissions after submission can amend their returns once through Tax-on-Web, but only until 15 July 2026.
