The 2042 form for the 2026 declaration campaign (2025 income) includes several technical modifications that deserve careful reading, even for taxpayers accustomed to online filing. Here, we detail the points that the 2026 practical brochure from the DGFiP does not always highlight.
AI Automated Suggestions on the 2042: What the 2026 Finance Law Changes
Law No. 2025-175 of December 30, 2025, introduced a system of AI-assisted pre-filling for non-pre-filled deductible expenses. In the pilot phase, this mechanism reduced declaration errors by 15%. Specifically, the online form now offers suggestions on certain expenses (notably medical expenses) that the taxpayer can either accept or reject.
This system does not exempt you from checking each line. The suggestions are based on data provided by third-party declarants and the household’s historical data. We recommend systematically cross-referencing these proposals with your supporting documents before validation, as an incorrectly accepted suggestion can lead to liability for your declaration.
To better understand the relationship between the cerfa 2042 for the 2026 tax declaration and its annexes, one must first master the logic of income allocation between forms.
Annexes 2042 C, 2042 RICI, 2042 C PRO: Income Allocation Criteria
The basic 2042 declaration (or 2042 K in pre-filled version) only covers salaries, pensions, and annuities. As soon as an income falls outside this scope, a specific annex is required. A common mistake is to report income on the wrong form, which triggers a request for justification from the administration.
Here is the technical breakdown to remember:
- 2042 C: income from movable capital, capital gains, real estate income under the actual regime. This is the annex most requested by taxpayers holding a securities portfolio or rental property.
- 2042 RICI: tax reductions and credits (donations to public interest organizations, childcare, contributions to a PER, home employment). Each tax credit has its own box and limit.
- 2042 C PRO: industrial and commercial profits (BIC), non-commercial profits (BNC), agricultural profits (BA). Essential for micro-entrepreneurs and liberal professions.
- 2042 IOM: overseas investments qualifying for tax reduction, with specific boxes depending on the scheme (industrial Girardin, social housing).
The 2044 (real estate income) and 2047 (foreign source income) complete this system but remain autonomous declarations, not annexes in the strict sense of the 2042.
Micro-Property or Actual Regime: A Choice Made on the 2042
The micro-property (flat-rate deduction of 30%) is declared directly on the 2042, box 4BE. The actual regime requires going through the 2044 and then transferring the result to the 2042 C. A taxpayer who exceeds the micro-property threshold and omits the 2044 is exposed to taxation on gross income, without expense deductions.
Tax Options on the 2042: PFU, Scale, and Actual Expenses
Three tax arbitrations structure the declaration and deserve a numerical analysis specific to each household.
The flat-rate withholding tax (PFU) at 30% applies by default to income from movable capital and capital gains from the sale of securities. Opting for the progressive income tax scale (box 2OP) may be more advantageous for households whose marginal tax rate remains below 30%. This option is global: it applies to all movable income of the household for the concerned year.
For salaries, the choice between the flat-rate deduction of 10% and the deduction of actual expenses (box 1AK) relies on a simple calculation. Actual expenses are only worthwhile if their total exceeds 10% of the taxable net salary. We observe that many taxpayers check this option without reaching this threshold, which increases their taxable base.
Online Declaration and Deadlines 2026: Impact on Tax Credit Refunds
Refunds related to tax credits declared via the 2042 RICI are processed on average ten days faster for online declarations compared to paper declarations, according to feedback from tax services reported by the Court of Auditors in its 2026 tax digitization report.
The paper version is only allowed in cases of inability to access the internet, with an earlier deadline (mid-May, compared to late May to early June for online filing depending on the department of residence). Beyond the refund deadline, online filing reduces the risk of input errors thanks to pre-filling and integrated consistency checks.
Correction After Submission: The Procedure to Know
An error identified after submission can be corrected online before the deadline without penalty. After this date, the online correction service generally opens during the summer and allows modification of most sections of the 2042 and its annexes. Any late correction outside these windows requires a contentious claim with the personal tax service.
The public finance centers report enhanced support at the counter since April 2026, especially for first-time filers (young people aged 18, new tax residents). This measure has helped reduce the rejection of paper declarations in this population.
The 2026 campaign does not disrupt the architecture of the 2042 form, but AI suggestions and the growing pressure towards dematerialization change the taxpayer’s stance. Checking each pre-filled box, arbitrating between PFU and scale, choosing the right property regime: these technical gestures remain the only safeguards against poorly calibrated taxation.
