You run your company from London, New York, Dubai or Singapore, and a French client asks your team to come and do the job on site in France: three engineers for a two-month installation near Lyon, a crew for a trade fair in Villepinte, a technician to repair a machine in Bordeaux. Flying people in looks simple, and many foreign managers treat it as a business trip. French law treats it as something else entirely: a posting of workers (détachement de salariés), a regulated operation with a prior declaration, a representative on French soil, French pay and working-time rules from day one, and fines that strike the foreign employer and the French client alike. The URSSAF (the network of offices that collects French social security contributions) can audit the operation, the labour inspectorate can walk onto the site, and the criminal courts punish concealed work (travail dissimulé) with prison terms and fines. This article explains, for a foreign founder or manager who stays abroad, the two papers that decide everything before the first day of work in France — the SIPSI declaration (the prior posting declaration filed on the SIPSI online portal, the posting-of-workers declaration system run by the Ministry of Labour) and the A1 certificate (the European social security certificate proving the worker stays covered at home) — and what happens, in fines, joint liability and criminal exposure, when the posting goes wrong, with the exact remedies you can run from abroad.
I. Before the first day on French soil, two papers decide everything
French law starts from a simple principle: any employer established outside France may temporarily post employees to France, provided an employment contract exists and the employment relationship continues during the posting. That is the wording of Article L1262-1 of the Labour Code: “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 same article lists the three posting patterns the law recognises: work performed for the employer’s own account under its direction within a contract with a French recipient, movement between establishments of the same company or group, and work performed for the employer’s own account with no French recipient at all. Your installation crew in Lyon falls under the first pattern, your intra-group transfer under the second, your trade-fair stand under the third — and all three trigger the same two formalities.
A. The SIPSI prior declaration and your representative in France
Before the posting starts, the foreign employer must file a prior declaration with the labour inspectorate (inspection du travail) of the place where the service begins. Article L1262-2-1 of the Labour Code states it in one sentence: the employer “adresse une déclaration, préalablement au détachement, à l’inspection du travail du lieu où débute la prestation.” In practice the declaration travels through the SIPSI teleservice (the posting-of-workers declaration system run by the French Ministry of Labour), and the official English guidance on service-public.fr confirms the mechanics: the declaration goes to the Departmental Directorate in charge of employment, labour and solidarity (the DDETS or DDETS-PP, the local arm of the labour administration that replaced the former Direccte units), and this declaration must be made before the beginning of the service. Filing on the SIPSI portal the morning the team lands is already late; the declaration must exist before the work starts, and each posting needs its own filing with the identity of the workers, the place, the dates and the nature of the service.
The second obligation surprises even careful managers: the foreign employer must appoint a representative of the company on French territory, tasked with liaising with the control officers for the whole duration of the service. The same Article L1262-2-1 provides that the employer “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.” This representative is not a mail drop. When inspectors arrive on the Lyon site, they call this person, and this person produces the papers. A foreign law firm with a Paris correspondent, a French client willing to act, or a specialised representative service can fill the role, but the designation must be real, reachable and documented before the posting begins, because an unreachable representative is treated almost like no representative at all.
One sentence of Article L1262-2-1 deserves to be read twice: “L’accomplissement des obligations mentionnées aux I et II du présent article ne présume pas du caractère régulier du détachement.” Filing the SIPSI declaration and appointing a representative do not presume that the posting itself is lawful. The declaration is a condition, not a shield. If the operation is in substance a permanent activity in France disguised as a posting, or a supply of labour outside the authorised patterns, the papers do not save it — and the fraud analysis, as the courts apply it, turns on the A1 certificate examined below and on the reality of the employer’s activity in its home State.
B. The A1 certificate and the European twenty-four-month rule
While SIPSI covers French labour law, the A1 certificate covers social security: it proves that the posted worker remains affiliated in the home State and that no French contributions are due during the posting. The legal basis sits in Article 12 of Regulation (EC) No 883/2004 on the coordination of social security systems, whose posting rule the Ministry of Labour recalls in its general framework for the posting of workers: the employer must normally carry out its activities in the home State, the foreseeable duration of the work abroad must stay within twenty-four months, and the worker must not be sent to replace another posted person. A letterbox company with no genuine activity at home cannot post, a rolling chain of workers replacing each other on the same French post breaks the rule, and a posting announced for thirty months fails the duration test from the start. The A1 must be requested from the home institution before or at the latest at the start of the posting, carried in practice on site, and matched to the real assignment: wrong dates, wrong State, wrong employer name on the certificate, and the protection evaporates.
When the A1 is genuine, its power is considerable. In a widely followed criminal ruling of 12 January 2021 (pourvoi No 18-86.757, published in the Bulletin), the Criminal Division of the Court of Cassation quashed a concealed-work conviction precisely because the trial judges had brushed aside Portuguese A1 certificates without going through the European dialogue procedure: the issuing institution must first be asked to review and withdraw the certificates in light of the fraud evidence, and only its failure to engage frees the French judge to disregard them. Read the official text on the website of the Court of Cassation (Criminal Division, 12 January 2021, pourvoi No 18-86.757, published in the Bulletin). The lesson for a foreign employer is direct: genuine A1 certificates, obtained for a genuine posting, bind the French judge — but certificates obtained or invoked fraudulently do not, once the home institution has been confronted with the evidence and refused to act. The Court confirmed the method again on 9 June 2026 (pourvoi No 24-85.090), holding that the dialogue and conciliation procedure of Regulation 883/2004 is a mandatory prerequisite before any final finding of fraud in the issuing of A1 certificates — official text on the website of the Court of Cassation (Criminal Division, 9 June 2026, pourvoi No 24-85.090, published in the Bulletin and the Report). Fraud can therefore be punished, but through the European procedure, not by shortcut.
From day one of a lawful posting, the posted workers must also receive the French hard core of employment rules. Article L1262-4 of the Labour Code requires the posting employer to guarantee the posted worker equality of treatment with employees of same-branch companies established in France — “lui garantit l’égalité de traitement avec les salariés employés par les entreprises de la même branche d’activité établies sur le territoire national” — across eleven matters including working time, rest, paid leave, health and safety, and pay within the meaning of Article L3221-3 “y compris les majorations pour les heures supplémentaires”, including overtime premiums. Concretely, your engineers in Lyon must be paid at least the French statutory or collectively agreed minimum for their category, with overtime premiums applied under French rules, housed and scheduled within French working-time limits, and reimbursed for posting-related travel, meal and accommodation costs. A salary that is comfortable at home but below the French sector minimum is a violation from the first payslip, and inspectors check payslips against the applicable collective agreement, not against the home-country contract.
II. When the posting goes wrong, the fines strike twice and the client pays with you
Posting violations are punished on two fronts at once: administrative fines calibrated per worker, and the criminal law of concealed work with joint liability that pulls the French client into the case. Understanding both layers before signing the French contract is what separates a manageable compliance cost from a dispute that swallows the margin of the whole deal. The amounts below are the statute in force, verified on the day of writing, and every figure your team circulates internally should be checked against these references rather than against blog posts or memories of older thresholds.
A. Your administrative fines, your client’s fines and the criminal risk behind them
Missing the SIPSI declaration, or missing the representative, or missing the information duties toward a temporary-work agency, exposes the foreign employer to an administrative fine pronounced by the administrative authority on a reasoned report of a labour inspector. Article L1264-3 of the Labour Code fixes the scale: “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 undeclared engineers therefore mean up to 40,000 euros on a first finding, doubled on a repeat finding within two years, with a 500,000-euro ceiling per decision. The authority must weigh the circumstances, the seriousness, the behaviour of the offender including good faith, and the resources and financial burdens of the company — so a first, documented, quickly corrected omission is not priced like a deliberate system — but the limitation period runs two full years from the day of the breach, and the fine is recovered like a State claim with no suspensive effect for opposition to enforcement. The same article closes the procedural door many foreigners expect: “L’employeur, le maître d’ouvrage ou le donneur d’ordre peut contester la décision de l’administration devant le tribunal administratif, à l’exclusion de tout recours hiérarchique” — challenge lies before the administrative court only, with no hierarchical appeal to the ministry.
The trap most foreign managers miss is that their French client is fined in parallel. Article L1264-2 of the Labour Code makes the project owner, the ordering party or the user company liable to an administrative fine under the same L1264-3 scale when its foreign contractor has not filed at least one of its SIPSI duties, when vigilance and information duties toward posted temporary workers are ignored, and when the user company’s own information duties fail: the client “est passible d’une amende administrative, dans les conditions prévues à l’article L. 1264-3” in each of these cases. Your Lyon client that never asked for your SIPSI receipt can therefore receive its own fine notice computed on your workers, and French purchasing departments know it — which is why serious French clients now demand the SIPSI acknowledgment and the A1 certificates before the team boards the plane, and suspend payment or site access until they arrive. A foreign contractor that answers slowly does not only risk its own fine; it puts its client’s money at risk, and the commercial relationship rarely survives the client’s fine.
Behind the administrative fines stands the criminal law of concealed work, and here the client’s exposure becomes personal. Every person concluding a contract for work, services or commerce must verify, when signing and periodically until performance ends, that its contractor complies with the registration and declaration formalities — Article L8222-1 of the Labour Code opens with “Toute personne vérifie lors de la conclusion d’un contrat” and the verification formalities are set by decree, which in practice means collecting the contractor’s registration proof, social-security compliance documents and, for a foreign poster, the A1 certificates. Anyone who skips this vigilance, and anyone convicted of using the services of a concealed-work operator, is held jointly liable with the offender: Article L8222-2 provides that such a person “est tenue solidairement avec celui qui a fait l’objet d’un procès-verbal pour délit de travail dissimulé” for taxes, social contributions, penalties, repayment of public aid, and the wages and payslip charges owed to the undeclared workers. Joint liability means the French tax office and the contribution collectors can pursue the solvent French client for the foreign contractor’s debts — the classic reason a French group terminates a foreign supplier at the first inspection report.
The Court of Cassation gave this vigilance duty teeth in a criminal ruling every foreign contractor should quote to its own management. On 21 February 2023 (pourvoi No 22-81.903, published in the Bulletin), the Criminal Division held that a legal person contracting with a company established in another European Union Member State must in all cases collect from that contractor the A1 certificate proving social compliance under Regulation (EC) No 883/2004 for every single posted worker used, and that a client who fails to verify the contractor’s situation and its ability to produce those certificates for all workers made available knowingly commits the offence of using the services of a concealed-work operator. Official text on the website of the Court of Cassation (Criminal Division, 21 February 2023, pourvoi No 22-81.903, published in the Bulletin). Note the practical standard: one missing A1 in a crew of twelve can support the finding, and “we trusted our contractor” is not a defence once the verification duty is established. Foreign founders who also operate through a French subsidiary should align the two sides of the house — the subsidiary, as a French client of the foreign parent’s posted teams, owes the same vigilance as any unrelated customer, a point developed in our guide to setting up a company in France as a foreign founder and in the analysis of choosing between a SAS, a SARL, a branch and a subsidiary.
Two further levers complete the picture and explain why inspectors are taken seriously on site. First, when a labour inspector finds a grave breach — daily or weekly rest ignored, maximum working time exceeded, legal or agreed minimum wage unpaid in whole or part, or working or housing conditions incompatible with human dignity — Article L1263-3 of the Labour Code empowers the inspector to order the employer in writing to end the situation: “il enjoint par écrit à cet employeur de faire cesser la situation dans un délai fixé par décret en Conseil d’Etat.” The inspector immediately informs the project owner or ordering party — “Il en informe, dans les plus brefs délais, le maître d’ouvrage ou le donneur d’ordre de l’employeur concerné” — so the client learns of the breach from the administration within days, and deliberately false information given to the inspector counts as a grave breach by itself: “Le fait pour l’employeur d’avoir communiqué à l’agent de contrôle des informations délibérément erronées constitue un manquement grave au sens du premier alinéa.” Second, ignoring an administrative decision once notified is punished separately: failure to comply with the decisions mentioned in Articles L1263-4, L1263-4-1 or L1263-4-2 carries an administrative fine of up to 10,000 euros per worker concerned, under Article L1263-6 of the Labour Code — “L’amende est inférieure ou égale à 10 000 € par salarié concerné par le manquement.” Defying a formal notice is therefore priced more than twice as high per head as the initial omission, which is why every notice must be answered within its deadline even while it is being challenged.
B. Inspections on site, documents in French and appeals you run from abroad
Controls arrive without warning, and the foreign employer must be ready in French. Article L1263-7 of the Labour Code requires the posting employer or its representative to present to the labour inspectorate, at the place of performance, documents translated into French that allow verification of compliance: the employer “présente sur le lieu de réalisation de la prestation à l’inspection du travail des documents traduits en langue française permettant de vérifier le respect des dispositions du présent titre.” Employment contracts or assignment letters, A1 certificates, SIPSI acknowledgment, representative designation, working-time records and payslips or pay statements must therefore exist in French versions on site — English originals alone do not satisfy the text, and a representative who promises to email translations next week concedes the breach on the spot. The documentary reflex should be built before departure: a posting file per worker, mirrored to the representative, updated with each rotation of staff, because inspectors return and compare filings across visits.
The URSSAF’s own control powers over foreign employers were confirmed at the highest level less than a year ago. On 16 October 2025 (pourvoi No 23-14.039, published in the Bulletin), the Second Civil Division of the Court of Cassation held that, to investigate or establish concealed-work offences concerning employees working in France for an employer headquartered abroad, the approved and sworn control officers of social-security bodies may, when investigating concealed work involving employees active in France for an employer headquartered abroad, verify the employer’s filing duties by collecting from that employer any documents, whatever their form or medium, showing whether it is affiliated with French social security — and it quashed a court of appeal that had annulled a reassessment on the ground that URSSAF officers could not demand posting documents from a company not established in France. Official text on the website of the Court of Cassation (Second Civil Division, 16 October 2025, pourvoi No 23-14.039, published in the Bulletin). A foreign company with no French establishment, no French payroll and no French registration is therefore still fully exposed to a URSSAF reassessment (redressement) on its posted workforce, and the resulting file often feeds the criminal investigation in parallel — the same facts priced twice, once in contributions and once in penalties. Our earlier analysis of URSSAF audits of French companies run from abroad describes the audit mechanics and the challenge routes that apply here as well.
In the Paris region the same rules run through the region’s own offices, and the practical details matter because most foreign postings land there: trade fairs at Villepinte, construction and IT projects in La Défense, installations across the inner suburbs. The SIPSI declaration designates the DDETS of the place where the service starts, so a posting beginning in Paris goes to the Paris administration and a posting beginning in Hauts-de-Seine to that department’s office — filing everything to a single contact because headquarters sits in the 8th arrondissement is a filing error, not a simplification. Site inspections in the region are carried out by the Paris-area labour inspectorate under the authority of the DREETS of Île-de-France (the regional directorate for the economy, employment, work and solidarities), whose officers concentrate precisely on sectors with heavy posting flows: construction, temporary work, trade fairs and events, transport and IT services. Foreign managers should therefore brief their representative on the exact site geography before each rotation, keep the French-language file at the actual place of work rather than at a Paris mailbox, and expect inspectors who know the standard evasion patterns of the sector — because in Île-de-France they see several each week.
When a fine or reassessment arrives at the foreign head office, the response clock starts under French rules and none of the steps require living in France. The administrative fine is challenged before the administrative court of the place of the decision, with no hierarchical appeal, within the standard two-month period running from notification — counsel in France files the recours, requests interim relief where the timetable allows, and builds the good-faith file: SIPSI receipts, A1 certificates, representative designation, French pay records and proof of rapid correction. The URSSAF reassessment follows its own adversarial procedure with observations, a response period and then the social-security court route, where the October 2025 ruling above sets the control-power framework both sides will argue within. The criminal track, finally, is where the A1 case law does its heaviest work: if A1 certificates exist, defence demands that the prosecution first trigger the European dialogue with the issuing institution, citing the January 2021 and June 2026 rulings, and refuses any shortcut finding of fraud; if no certificates exist, the effort shifts to contesting the concealed-work characterisation itself, the knowledge element, and the computation of the alleged damage. In every track, the documents that win are the ones created before the control, not after it — which returns the whole strategy to the two papers of Part I, filed on time, in French, and kept consistent across SIPSI, A1 forms and payslips.
Conclusion
Sending your own staff to work in France is never a mere trip: it is a posting governed by a prior SIPSI declaration to the labour administration of the place of performance, a reachable representative on French soil, genuine A1 certificates within the European twenty-four-month framework, and French pay, time and safety rules from the first hour. The price of improvisation is measured per worker — up to 4,000 euros per posted employee, 8,000 on a repeat finding, capped at 500,000 euros — and doubled across the table, because the French client faces its own fines, its own vigilance trial and joint liability for your contributions and wages. The courts have drawn the lines clearly: genuine A1 certificates bind the French judge until the European dialogue says otherwise, missing A1 certificates expose the client to a criminal concealed-work finding, and URSSAF officers may demand posting documents even from employers with no French establishment. File before departure, translate everything into French, keep the representative reachable, pay the French minima with their overtime premiums, and answer every notice within its deadline while challenging it before the right court. A posting prepared this way costs a few days of paperwork; a posting improvised this way can cost the contract, the client and, in the worst cases documented above, a criminal record.