You run a company in London, New York, Dubai or Singapore and you need your own people working in France for a few weeks or months: installing equipment, supervising a building site, opening a showroom, training a distributor’s team. Incorporating a French subsidiary feels premature and hiring under a French employment contract feels disproportionate for a short mission. French law offers a third way that foreign founders often discover too late: posting your existing staff to France, known in French law as détachement. The mechanism is perfectly lawful, but it is strictly conditional. Before your employees set foot on the French site, you must file a prior declaration with the French labour inspectorate through the SIPSI portal (Système d’information sur les prestations de service internationales, the official online declaration system for international postings), appoint a representative based in France, and secure an A1 social-security certificate for each worker. Once they are here, French minimum pay, working time and safety rules apply to them almost in full, and after twelve months the French Labour Code applies nearly entirely. The sanctions for skipping these steps are severe: administrative fines of up to 4,000 euros per posted worker, joint liability for unpaid wages with your French client, URSSAF (Unions de recouvrement des cotisations de sécurité sociale et d’allocations familiales, the agencies that collect French social-security contributions) reassessments, and even criminal prosecution for hidden work. This guide explains, step by step, how to post staff to France lawfully from abroad, what an A1 certificate really protects you against after the landmark Bouygues rulings, and how to react if the inspectorate or URSSAF knocks on your door.

I. Lawfully posting your staff to France: the three legal routes, the prior SIPSI declaration and the A1 certificate

A. Intra-group secondment, cross-border service contracts and agency postings: choose the right route, then declare before day one

French law starts from a simple definition. Article L1261-3 of the Labour Code provides: «Est un salarié détaché au sens du présent titre tout salarié d’un employeur régulièrement établi et exerçant son activité hors de France et qui, travaillant habituellement pour le compte de celui-ci hors du territoire national, exécute son travail à la demande de cet employeur pendant une durée limitée sur le territoire national dans les conditions définies aux articles L. 1262-1 et L. 1262-2 .» Three cumulative conditions already appear in that single sentence: your company must be genuinely established and genuinely active outside France, the worker must normally work for you outside France, and the mission in France must be for a limited time. A letterbox company with no real activity abroad, or a worker recruited the day before the mission who never worked in your home office, fails the test from the outset, and everything that follows collapses.

Article L1262-1 of the Labour Code then sets the framework: «Un employeur établi hors de France peut détacher temporairement des salariés sur le territoire national, à condition qu’il existe un contrat de travail entre cet employeur et le salarié et que leur relation de travail subsiste pendant la période de détachement.» The employment relationship must survive the posting: the worker remains your employee, paid by you, subordinate to you. The same article offers three routes. First, posting performed for your own account under your direction within a contract concluded with a French client (the classic cross-border service: you sell installation, maintenance or consulting and send your technicians). Second, posting between establishments of the same company or between companies of the same group (the intra-group secondment: your German parent sends engineers to its French subsidiary, or your British head office sends a manager to open the Paris branch). Third, posting for your own account without any contract with a recipient (for example your own staff working on your own French project). Temporary-work agencies established abroad have their own parallel regime under article L1262-2, which allows them to place posted agency workers with a French user company or with a foreign user company operating temporarily in France.

Choosing the route matters because the paperwork and the risks differ. In a service contract or an agency posting, your French client carries its own legal duties toward you, examined below, and will ask for your papers before signing. In an intra-group secondment, there is no outside client, but the French host entity still faces the inspectorate if your file is incomplete. In every case except the narrow own-account route without a recipient, the same prior formality applies, and it is non-negotiable. Article L1262-2-1 of the Labour Code states: «L’employeur qui détache un ou plusieurs salariés, dans les conditions prévues aux 1° et 2° de l’article L. 1262-1 et à l’article L. 1262-2 , adresse une déclaration, préalablement au détachement, à l’inspection du travail du lieu où débute la prestation.» In practice this is the SIPSI declaration, filed online before the mission starts with the labour inspectorate (inspection du travail, the administration that polices labour law) of the place where the work begins. The same article adds a second duty: «L’employeur mentionné au I du présent article désigne un représentant de l’entreprise sur le territoire national, chargé d’assurer la liaison avec les agents mentionnés à l’article L. 8271-1-2 pendant la durée de la prestation.» You must therefore designate a contact person physically reachable in France for the whole mission, able to produce documents during an inspection. Many foreign companies ask their French lawyer, their accountant or the host subsidiary to fill this role under a written mandate.

Two practical warnings follow. First, filing the declaration does not whitewash an artificial arrangement. The statute says so expressly in article L1262-2-1: «L’accomplissement des obligations mentionnées aux I et II du présent article ne présume pas du caractère régulier du détachement». Inspectors look at substance: real activity abroad, pre-existing employment relationship, temporary mission, genuine link of subordination maintained with you. Second, keep a complete file available on site and in French or with translations: employment contracts, A1 certificates, the SIPSI receipt, the representative’s mandate, pay records and working-time records. Inspections on construction sites and in logistics hubs are frequent, unannounced, and document-driven; the company that produces everything within the hour is treated very differently from the one that promises to email it from headquarters next week. If your presence in France is not temporary at all but permanent, posting is the wrong tool altogether: you should instead choose between a French subsidiary and a branch and register it properly.

B. Staying under home-country social security with an A1 certificate, and understanding what that certificate does not protect

French social charges are heavy, around 42 to 45 percent of gross salary at employer level for a standard profile, so every foreign founder asks the same question: must posted workers join the French social-security system and pay French contributions? Within the European Union, the European Economic Area and Switzerland, the answer is normally no for temporary postings, thanks to the coordination rules of Regulation (EC) No 883/2004 on the coordination of social security systems. Its Article 12 allows a worker sent by an employer to another Member State to remain subject to the home State’s legislation for up to 24 months, provided the worker is not sent to replace another posted worker. The home institution documents this with an A1 certificate, formerly called E101. You apply in your home country before the mission, you keep paying home-country contributions, and in principle URSSAF cannot claim French contributions for the same period. The mirror situation under French law confirms the logic: the Cour de cassation held on 13 October 2022 (Second Civil Chamber, appeal no. 21-13.252) that «s’ils ne sont pas ou ne sont plus soumis à la législation française de sécurité sociale en vertu de conventions ou de règlements internationaux, les travailleurs détachés temporairement à l’étranger par leur employeur pour y exercer une activité salariée ou assimilée, rémunérée par cet employeur, sont soumis à la législation française de sécurité sociale à la condition que l’employeur s’engage à s’acquitter de l’intégralité des cotisations dues auprès de la caisse d’affiliation du salarié». In other words, posting is a two-way bridge: the worker stays affiliated at home and the employer keeps paying there, on both sides of the border.

But here lies the costliest misunderstanding in this entire field: many employers treat the A1 certificate as a general immunity pass covering labour law too. It is not, and the highest French criminal court said so in the most commented posted-workers case of the decade. After an investigation on the Flamanville reactor building site revealed posted workers with deficient cover, undeclared accidents and substandard conditions, the Criminal Chamber of the Cour de cassation ruled on 12 January 2021 (appeal no. 17-82.553, Bouygues travaux publics) that the main contractor and its subcontractors could be convicted of recourse to hidden work and unlawful lending of labour despite holding E101 and A1 certificates, with fines of 29,950, 60,000 and 15,000 euros. Endorsing the answer given by the Court of Justice of the European Union on 14 May 2020 (C-17/19), the Court held that such certificates bind the courts of the host State «uniquement en matière de sécurité sociale», quoting the CJEU’s own words: «les certificats E101 et A1, délivrés par l’institution compétente d’un État membre, ne lient l’institution compétente et les juridictions de l’État membre d’accueil qu’en ce qu’ils attestent que le travailleur concerné est soumis, en matière de sécurité sociale, à la législation du premier État membre», so that «ces certificats ne produisent donc pas d’effet contraignant à l’égard des obligations imposées par le droit national dans des matières autres que la sécurité sociale, au sens de ces règlements, telles que, notamment, celles relatives à la relation de travail entre employeurs et travailleurs, en particulier, les conditions d’emploi et de travail de ces derniers». Concretely: a valid A1 blocks a French social-security reassessment, but it does not block a criminal conviction for undeclared work, underpaid wages or unlawful labour lending, and the labour inspector’s findings on pay and working conditions stand regardless of the certificate.

Outside the EU-EEA-Switzerland zone, the analysis is bilateral and often harsher. France has signed social-security treaties with some forty countries, including the United States, Canada, the United Kingdom under the Trade and Cooperation Agreement’s protocol, Morocco, Algeria, Tunisia, Israel, Japan, South Korea, Brazil and others, each with its own scope and maximum posting duration; some cover only pensions, others exempt the worker from French sickness and retirement contributions for a defined period upon presentation of a certificate of coverage. Where no treaty applies, there is no posting shield at all: the worker falls under French social security from day one, you must register with URSSAF and pay French contributions, and the cost of the mission must be budgeted accordingly. Before promising a client a start date, map each worker’s nationality, home affiliation, treaty coverage and certificate lead time. An A1 within the EU is typically obtained in days or weeks from the home institution; a posting with no certificate and no treaty is a French payroll from the first payslip, and discovering this after the mission has started is how reassessments are born.

II. Once your staff work on French soil: the equal-treatment rules, the papers to hold ready, and the price of mistakes

A. French pay and working-time rules, a reachable local representative, payslips, and your French client’s duty to check your papers

Posted workers are not a cheap parallel workforce: France applies to them the hard core of its labour law on an equal-treatment basis. Article L1262-4 of the Labour Code provides that the posting employer «lui garantit l’égalité de traitement avec les salariés employés par les entreprises de la même branche d’activité établies sur le territoire national», and then lists the protected matters: individual and collective freedoms, non-discrimination and equality between women and men, maternity and paternity protection, temporary-work guarantees, the right to strike, working time, compensatory rest, public holidays, paid holidays, health and safety, and, crucially, «8° Rémunération au sens de l’article L. 3221-3 , paiement du salaire, y compris les majorations pour les heures supplémentaires», plus reimbursement of posting-specific travel, meal and accommodation expenses. In plain terms, your posted electrician on a Lyon building site must receive at least the French statutory minimum wage (SMIC) or the higher minimum set by the applicable sector-wide collective agreement, overtime premiums, paid leave accrual and the same safety equipment and training as a French colleague. Since the 2018 reform of the EU posting directive, transposed into this article, allowances specific to the posting count toward the minimum only under defined conditions, while genuine expense reimbursements do not: mixing the two lines on the payslip is one of the most frequent findings in inspections.

Time deepens the obligation. For postings longer than twelve months, the same article L1262-4 provides that the employer becomes subject, from the thirteenth month, to nearly all the provisions of the Labour Code applicable to companies established in France, with only narrow exceptions; where a posted worker is replaced by another posted worker on the same post, the twelve months accumulate. A mission initially planned for eight months that silently stretches to fourteen therefore changes legal regime mid-course, importing French rules on matters well beyond the initial hard core. Calendar discipline matters: set a written end date, track cumulative durations per post, and decide before month twelve whether to rotate lawfully, convert to local employment or incorporate. If rotation is artificial, inspectors and judges treat successive postings on the same post as a single posting, and the reclassification follows.

Formally, two figures structure every compliant posting. On your side, the local representative designated under article L1262-2-1 must be reachable throughout the mission and able to liaise with control officers and produce documents: many founders mandate their French counsel or accountant in writing, with a defined scope and fee, rather than improvising with the client’s reception desk. Each worker should carry or have immediately available proof of the SIPSI declaration, the A1 certificate, the employment contract, medical fitness where required for risky work, and working-time records. Payslips must exist and be correct: article L3243-2 of the Labour Code states that «Lors du paiement du salaire, l’employeur remet aux personnes mentionnées à l’article L. 3243-1 une pièce justificative dite bulletin de paie», and inspectors cross-check declared hours against badge, gate and planning data. A payslip showing 35 hours where site logs show 50 is not a clerical error in the inspector’s eyes; combined with the criminal definition of hidden work by understated hours, it becomes an intentional offence, as examined below.

On the French client’s side, the law turns your customer into your controller. Article L1262-4-1 of the Labour Code requires the client or project owner contracting with a posting service provider to verify, before the posting begins, that the provider has completed the SIPSI declaration and the representative designation; failing that, the client must itself file a declaration with the labour inspectorate within forty-eight hours of the start of the posting, and must also verify that the provider has paid any posting-related administrative fines already imposed. The general vigilance duty reinforces this: article L8222-1 of the Labour Code provides that «Toute personne vérifie lors de la conclusion d’un contrat dont l’objet porte sur une obligation d’un montant minimum en vue de l’exécution d’un travail, de la fourniture d’une prestation de services ou de l’accomplissement d’un acte de commerce, et périodiquement jusqu’à la fin de l’exécution du contrat, que son cocontractant s’acquitte : 1° des formalités mentionnées aux articles L. 8221-3 et L. 8221-5», the two criminal definitions of hidden work. Expect therefore a competent French client to demand your SIPSI receipt, your representative’s details, your A1 certificates and a sworn statement of compliance before your team arrives, and to repeat the checks during the contract. Prepare that file once, keep it updated, and you will shorten every commercial negotiation; arrive without it, and serious clients will simply choose a compliant competitor.

B. Administrative fines per worker, joint liability for wages, URSSAF reassessment and criminal prosecution: the sanctions chain and how to react from abroad

The sanctions chain starts with the labour inspectorate and its administrative fines. Article L1264-2 of the Labour Code makes the client, the project owner or the user company liable to an administrative fine where its contractor failed the SIPSI declaration or the related duties and the client did not perform its own verification and fallback declaration. The amounts are set by article L1264-3: «Le montant de l’amende est d’au plus 4 000 € par salarié détaché et d’au plus 8 000 € en cas de réitération dans un délai de deux ans à compter du jour de la notification de la première amende. Le montant total de l’amende ne peut être supérieur à 500 000 €.» Ten undeclarated workers on a first finding can therefore cost up to 40,000 euros, and a repeated finding within two years doubles the per-worker ceiling, with the authority calibrating the amount to the circumstances, the gravity, the good faith of the offender and its resources. Both sides of the contract are exposed at once: you as the posting employer for your own declaration failures, and your French client for failing to check you, which is why clients now push the compliance file upstream before signature.

The second link is financial solidarity for wages. Where a posted worker is not paid at least the French legal or collectively agreed minimum, and the control officers have formally notified the client, article L1262-4-3 of the Labour Code requires the client or project owner to order the contractor in writing to end the situation immediately; failing regularization within the regulatory deadline, «le maître d’ouvrage ou le donneur d’ordre, s’il ne dénonce pas le contrat de prestation de service, est tenu solidairement avec l’employeur du salarié au paiement des rémunérations, indemnités et charges dues». A French client that turns a blind eye to underpaid posted workers can thus end up paying your wage arrears, holiday pay and related charges alongside you, unless it terminates the service contract. Commercially, this means underpayment clauses, audit rights and termination rights in your service agreements are not boilerplate: they allocate a liability that the statute imposes by default, and sophisticated clients will insist on them.

The third link is social-security reassessment by URSSAF, and foreign employers systematically underestimate it. Where the posting is irregular, the A1 missing or the treaty inapplicable, URSSAF treats the workers as subject to French contributions and reassesses several years of contributions with surcharges, a procedure whose contradictory stages and remedies are described in our guide to URSSAF audits of foreign-owned companies. A very recent ruling strengthens the agency’s hand where hidden work is involved: on 16 October 2025 the Second Civil Chamber of the Cour de cassation (appeal no. 23-14.039) quashed a Court of Appeal decision that had annulled a reassessment built on hidden-work findings against a Portuguese company, recalling the statutory definitions word for word. The Court restated that «est réputé travail dissimulé par dissimulation d’emploi salarié le fait pour tout employeur : 1° Soit de se soustraire intentionnellement à l’accomplissement de la formalité prévue à l’article L. 1221-10 du code du travail, relatif à la déclaration préalable à l’embauche», that same pre-hiring declaration (DPAE, déclaration préalable à l’embauche) which article L1221-10 makes a precondition of any hiring: «L’embauche d’un salarié ne peut intervenir qu’après déclaration nominative accomplie par l’employeur auprès des organismes de protection sociale désignés à cet effet.» The lesson for posting employers is direct: missing declarations and missing payslips feed both the labour-criminal case and the URSSAF reassessment, and winning on one front does not close the other.

The fourth link is criminal. Hidden work by concealment of activity and by concealment of employment are defined by articles L8221-3 and L8221-5 of the Labour Code: operating for profit while intentionally evading registration or social and tax declarations, or, as an employer, intentionally evading the pre-hiring declaration, payslips, or wage and contribution returns, including by understating hours on the payslip. Penalties are set by article L8224-1: «Le fait de méconnaître les interdictions définies à l’article L. 8221-1 est puni d’un emprisonnement de trois ans et d’une amende de 45 000 euros.» Individuals also face additional penalties under article L8224-3, including «2° L’exclusion des marchés publics pour une durée de cinq ans au plus». The Bouygues case recalled above shows these provisions applied to posted workers on a major French site, with custodial-risk prosecution of managers alongside corporate fines. Unlawful lending of labour (marchandage and prêt illicite de main-d’oeuvre) often joins the charges where posted workers in fact work under the client’s exclusive direction while the foreign employer is a mere mailbox: at that point the posting is reclassified as a sham, the workers are deemed the client’s employees, and dismissal, back-pay and seniority consequences follow under French employment law. If a mission must end, the exit must itself follow French dismissal rules, on which our guide to dismissing a first employee from abroad gives the procedure.

If you are targeted from abroad, react in the right order. First, secure the representative and the documents: an inspector who receives the file within hours often limits the finding to a warning or a single fine rather than a site-wide investigation. Second, regularize immediately: file the late SIPSI declaration, top up wages to the applicable minimum, issue corrected payslips and pay the missing contributions spontaneously, because demonstrated good faith weighs expressly in the calibration of the fine under article L1264-3 and in later negotiations. Third, never ignore a notification: administrative fines, formal notices to regularize and URSSAF observation letters all run on short appeal deadlines, and silence converts a contestable claim into an enforceable debt. Fourth, coordinate the fronts: the same facts feed the inspector’s fine, the client’s solidarity claim, the URSSAF reassessment and potentially the prosecutor, so statements made hastily on one front bind you on the others. A lawyer in France can centralize the file, appoint or serve as representative, handle the inspectorate and URSSAF in French, and sequence appeals so that a victory on the declaration front is not wasted by a default on the contributions front.

Conclusion

Posting your own staff to France without hiring locally is lawful and often the smartest first step: pick the correct route among service contract, intra-group secondment and agency posting, file the SIPSI declaration before day one, designate a reachable representative in France, and secure an A1 certificate or treaty coverage for every worker. On site, apply French minimum pay, working time and safety rules as equal treatment requires, watch the twelve-month threshold that imports nearly the whole Labour Code, and hand your French client the compliance file it is legally bound to demand. Remember the two hard lessons of the case law: an A1 certificate shields you in social-security matters only and never against hidden-work prosecution, and missing declarations feed fines, wage solidarity, URSSAF reassessment and criminal charges at the same time. Run through this checklist before each mission, and a short French assignment stays what it should be: a commercial opportunity, not a multi-front dispute managed from another time zone.

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