Déclaration de revenus & Liasse fiscale - Calendrier

2025 income tax return

The 2026 filing season for 2025 income will open on 9 April 2026.

The online filing service will remain open until the following deadlines, set by département:

• Zone 1 (01 to 19 and non-residents): Thursday 21 May 2026 (11.59 pm);
• Zone 2 (20 to 54): Thursday 28 May 2026 (11.59 pm);
• Zone 3 (55 to 976): Thursday 4 June 2026 (11.59 pm).

Online filing is mandatory for all taxpayers whose main residence has Internet access. However, for taxpayers still using the paper form because they are "too far removed from digital technology", the deadline is brought forward to 19 May 2026.

If the income tax return is filed late, the tax will be increased by 10%.

The surcharge rises to 20% if the return is filed late within 30 days of a formal notice from the Tax Authorities.

In certain situations, heavier penalties apply:

• 40% where the return has not been filed within 30 days of receipt of a formal notice
• 80% where an undeclared activity is discovered, without the need for a formal notice.

Late-payment interest will also be charged. It amounts to 0.20% of the tax due per month of delay (i.e. 2.4% over one year). This interest applies until the last day of the month in which the income tax return is filed.

Corporate tax return for the 2025 financial year

- Companies closing their financial year on 31 December 2025

The deadline for filing the corporate tax return is set at the second business day following 1 May. For 2026, this second business day falls on 3 May, a Sunday, which postpones the statutory deadline to 5 May 2026.

However, the Tax Authorities grant an additional period of 15 calendar days to any company that files electronically. The deadline for filing the corporate tax return is thus postponed to 20 May 2026.

In addition, the calculation and electronic payment of the balance of corporate income tax must in principle take place no later than 15 May 2026.

- Companies subject to corporate income tax closing their financial year on another date during the year

A company whose financial year does not coincide with the calendar year has 3 months from the financial year-end to file its corporate tax return.

However, the Tax Authorities grant an additional period of 15 calendar days to any company that files electronically.

In addition, the balance must be paid electronically no later than the 15th of the fourth month following the financial year-end.

Failure to meet the deadline for filing the corporate tax return gives rise to interest of 0.20% of the tax due per month of delay (i.e. 2.4% over one year). A surcharge of between 10% and 80% of the tax may also be applied:

• 10% surcharge on the tax due in the absence of a formal notice, or where the return is filed within 30 days of receipt of a formal notice;
• 40% surcharge where the return is not filed within 30 days of the formal notice;
• 80% surcharge where an undeclared activity is discovered.