Overview
- Paper filers, who must post by Tuesday at midnight, can rely on the La Poste postmark to prove the deadline was met.
- Online filers face staggered cutoffs at 23:59 by department number: 01–19 and non‑residents on Thursday 21 May, 20–54 on Thursday 28 May, and 55–974/976 on Thursday 4 June.
- Filing online is compulsory for households that have internet access and can complete the process on impots.gouv.fr.
- Missing the date leads to a 10% surcharge that can rise to 20% after a formal notice and 40% if the delay persists, with interest of 0.2% of the tax due per month and up to 80% in cases of undisclosed activity.
- More than 10 million households receive an automatic pre‑filled return that needs no action if the information is correct.