DSN 2026: Complete Guide to France's DSN Social Declaration

The DSN must be filed before noon on the 5th of the following month by employers with at least 50 employees whose payroll is paid within the work month, and on the 15th in all other cases (article R243-6 CSS). If the deadline falls on a Saturday, Sunday or public holiday, it moves to the next working day.

Short answer: the DSN (Déclaration Sociale Nominative) has been mandatory for all French employers since January 2017. In 2026, it remains the single channel for transmitting social declarations to URSSAF, pension funds and health insurance bodies. This guide explains the calendar, technical requirements, common pitfalls and penalties.

The DSN is a monthly electronic declaration that progressively replaced all annual and monthly social declarations by employers. Its threefold objective is:

1. Simplify procedures: one single declaration replaces dozens of paper forms
2. Improve data reliability: real-time transmission of social information
3. Accelerate processing: automated calculation of contributions and employee rights

In 2026, the DSN applies to all businesses employing at least one employee, regardless of headcount. Self-employed individuals without employees are not subject to DSN.

The legal framework is based on Article L.133-5-3 of the French Social Security Code, created by article 35 of Law no. 2012-387 of 22 March 2012 and amended by Ordinance no. 2015-682 of 18 June 2015 on the simplification of employers' social declarations. The reference platform is net-entreprises.fr, run by the GIP-MDS (the public interest grouping for the modernisation of social declarations); ACOSS, often cited by mistake, became Urssaf Caisse nationale in 2021.

Practical implications for employers#

The DSN is not just an administrative formality. It directly affects:

• Calculation and payment of social contributions (URSSAF, Agirc-Arrco, supplementary pension funds)
• Employee affiliation to social protection schemes
• Validation of rights to retirement, unemployment benefits and professional training
• Payment of daily allowances in case of illness or maternity

An error or delay in the DSN can therefore have direct consequences on employee rights and on the company's financial situation.

The DSN is filed every month, before a deadline set by article R243-6 of the French Social Security Code. There is not one date but two: the 5th of the following month for employers with at least 50 employees whose payroll is paid within the work month, and the 15th of the following month in all other cases (fewer than 50 employees, or 50 and more with payroll paid in the following month). Filing must be completed before noon, and a deadline falling on a Saturday, Sunday or public holiday moves to the next working day.

The table already includes the postponements: 5 April 2026 is a Sunday followed by Easter Monday (6 April), so the March DSN moves to Tuesday 7 April 2026; 15 August 2026 is a Saturday public holiday, so the deadline moves to Monday 17 August 2026.

Important: your deadline depends on your headcount and on whether payroll is paid in the following month, not on a company choice. Check it in your account on net-entreprises.fr. Note also that the monthly DSN must be filed even where no remuneration has been paid, for as long as the employer has not requested the closure of its account (article R133-14 of the French Social Security Code).

Real-time event reporting: DSN for employment termination#

Beyond the monthly declaration, the DSN allows real-time reporting of the following events:

• End of employment contract: since 1 January 2022 the single end-of-contract report (FCTU) is the only filing route. It must be sent within 5 days of the end of the contract and produces the rematerialised employer certificate (AER) handed to the employee (Pôle emploi became France Travail on 1 January 2024)
• Sick leave, maternity, paternity leave: report within 5 days of becoming aware of the leave, replacing the paper salary certificate
• Sick leave following a work accident: only the leave report goes through the DSN. The work accident declaration (DAT) is filed outside the DSN, through the dedicated service of the company account on net-entreprises.fr, within 48 hours excluding Sundays and public holidays (article R441-3 of the French Social Security Code)

The prior declaration of hiring (DPAE), often listed alongside these, is not a DSN: it is filed separately with URSSAF.

These real-time reports are integrated into the DSN via the "events" block and must be transmitted within regulatory timeframes.

Step 1: Initial setup and certified software#

Before producing a DSN, the employer must ensure that their payroll software is DSN-certified. Compliance resources (the DSN-Val self-check tool, the software vendor qualification portal and the certificate of conformity) are published by the GIP-MDS on net-entreprises.fr and dsn-info.fr, not by ACOSS. Payroll solutions that actually issue DSN filings include:

• Silae (widely used by chartered accountants)
• Cegid
• Sage Paie
• PayFit
• ADP, Nibelis, Openpaye

Switching to new payroll software involves a data migration phase. Our firm's recommendation, not a legal rule, is to plan it 3 to 6 months before going live.

Step 2: Monthly declaration, mandatory blocks#

A monthly DSN contains several data blocks:

Employer block:

• SIRET (the DSN is filed per establishment, not per SIREN), NAF code, company name
• Headcount and payroll amount
• Number of employees joining and leaving

Employee block (for each employee):

• Social security number (NIR)
• Date of birth, nationality
• Gross remuneration detail (employer and employee portions)
• Hours worked (for contribution calculation)
• Provident fund and mutual insurance
• Daily allowances

Contributions block:

• Split between employer and employee portions
• Contribution rates by scheme
• Contribution base

Step 3: Exceptional event reporting#

Between monthly declarations, certain events must be reported immediately:

• End of contract: the FCTU report produces the rematerialised employer certificate (AER) handed to the employee. It must be sent within 5 days of the end of the employment contract, and not with the following month's DSN.
• Work stoppage: the report must be issued within 5 days of becoming aware of the leave, via the "work stoppage signal" block of the DSN.
• Work accident: the work accident declaration is filed on the dedicated service of net-entreprises.fr, within 48 hours excluding Sundays and public holidays; the DSN only carries the resulting sick leave report.

Since 2017, the DSN has progressively replaced the following declarations:

For employers, the DSN represents significant time savings. For chartered accountants, it simplifies the payroll production process and reduces the risk of manual entry errors.

DSN errors are frequent and can have significant financial consequences. Here are the most common pitfalls:

Mistake 1: Incorrect or unverified Social Security number#

The NIR (national identification number) has 13 digits followed by a 2-digit check key, equal to 97 minus the remainder of those 13 digits divided by 97: it is a modulo 97 calculation, not the Luhn algorithm. An invalid NIR blocks the declaration and can cause the entire DSN to be rejected. It is imperative to systematically verify the NIR upon hiring.

Mistake 2: Incorrect classification of remuneration#

Not all remuneration is subject to the same contributions. Confusing an exceptional bonus with a salary supplement, or forgetting to include benefits in kind, creates discrepancies between the DSN and the payroll ledger and may trigger a URSSAF audit.

Mistake 3: Incorrect reporting of overtime hours#

Since the reform introduced by article 7 of the 2019 Social Security Financing Act (Law no. 2018-1203 of 22 December 2018) and article 2 of Law no. 2018-1213 of 24 December 2018, implemented by Decree no. 2019-40 of 24 January 2019, overtime and additional hours must be declared separately in the DSN. Incorrect allocation deprives the employee of the reduction in employee old-age insurance contributions, capped at 11.31% (article D241-21 of the French Social Security Code).

Mistake 4: Inconsistent contract dates#

A contract start date after the pay date, or an end date before the declared pay period, generates a technical rejection of the DSN. Always check the consistency of dates before transmission.

Mistake 5: Forgetting the DPAE (prior declaration of hiring)#

The former DUE no longer exists: it was merged into the DPAE on 1 August 2011 (Decree no. 2011-681 of 16 June 2011). The DPAE is filed with URSSAF at the earliest within the 8 days preceding the expected hiring date and, electronically, at the latest in the moments preceding the start of work (articles R1221-4 and R1221-5 of the French Labour Code). Failure to file carries a penalty equal to 300 times the hourly minimum guaranteed wage (article L1221-11 of the Labour Code) and may be treated as undeclared work (article L8221-5).

URSSAF has automated control tools that continuously analyse DSNs. Controls focus notably on:

• Consistency of declared headcount vs. actual headcount
• Average contribution rate per employee vs. sectoral norms
• Significant discrepancies between two consecutive months
• Work stoppage reports: abnormally high rates, atypical durations
• Final pay statements: amounts inconsistent with the employee's profile

In case of detected anomaly, URSSAF may send a preliminary observation letter before any formal demand. The observation letter opens the adversarial period of article R243-59 of the French Social Security Code: the employer has 30 days to respond and provide supporting documents, extended to 60 days on request, silence from the body counting as acceptance.

Hayot Expertise advice: we recommend a quarterly consistency review of the DSN, comparing declared data with the payroll ledger. This review detects and corrects anomalies before they are flagged by URSSAF.

What a late or inaccurate DSN costs in 2026#

The amounts below are based on the monthly social security ceiling (PMSS), set at 4,005 euros for 2026.

Businesses with several establishments must produce one DSN per establishment, using each establishment's SIRET as identifier. The DSN filings of all establishments of a single company can, however, be grouped in one deposit file, which then contains as many monthly DSN filings as there are establishments, each identified by its own SIRET.

For groups of companies, the DSN does not replace consolidated declarations at group level (particularly for the contribution base).

Hayot Expertise ensures complete payroll production and monthly DSN transmission:

• Initial setup of your payroll software and DSN certification
• Monthly production of payslips and DSN
• Real-time reporting of events (stops, contract terminations)
• Quarterly consistency review before transmission
• Correction management: cancel-and-replace before the deadline, adjustment blocks afterwards

Discover our complete payroll offering on our pricing page

The DSN is a major simplification lever for employers, provided it is properly mastered. In 2026, automated URSSAF controls make declaration quality even more critical. One misplaced click or an inconsistent date can trigger an audit procedure. Support from a chartered accountant secures your declarations, corrects errors in real time and preserves your employees' rights.

One last safeguard: article R243-11 of the French Social Security Code provides a right to make a mistake. Late payment surcharges and penalties are not due if the contributor puts the position right within 30 days, no delay was recorded over the preceding 24 months and the amount of the surcharges stays below the monthly social security ceiling.