When May a Host State Court Disregard an A1 Certificate? The French Court of Cassation Clarifies

An A1 certificate generally provides important legal certainty for employers and workers involved in cross-border assignments within the EU. In a recent decision, the French Court of Cassation clarified when a host State court may nevertheless disregard an A1 certificate where there is concrete evidence of fraud.

Here, CELIA Alliance’s French member firm Galahad Avocats examines the judgment and its implications for employers managing posted workers, international assignments and cross-border social security arrangements.

An A1 certificate normally binds the authorities and courts of the Member State in which a worker performs an activity. 

In a decision delivered on June 9, 2026, the Criminal Chamber of the French Court of Cassation clarified when a host State court may nevertheless disregard such a certificate in a case involving fraud. 

The judgment is particularly relevant for employers involved in cross-border assignments, international mobility teams and companies using workers posted to France. It confirms the protective effect of the A1 certificate, while also defining what the issuing institution must do when concrete evidence of fraud is submitted to it. 

The A1 certificate remains binding in principle

An A1 certificate identifies the social security legislation applicable to a person working in a cross-border situation within the European Union. In a posting situation, it generally confirms that the worker remains subject to the social security system of the sending State. 

Based on the principles of sincere cooperation and mutual trust between Member States, an A1 certificate creates a presumption that the worker's affiliation to the issuing State's social security system is lawful. The authorities and courts of the host State must therefore respect it for as long as it has not been withdrawn or declared invalid by the issuing institution. 

This remains the starting point even where the host State considers that the factual conditions for issuing the certificate were not met. 

The facts considered by the Court

The case concerned a company initially established in Spain that supplied workers to agricultural businesses in France. The workers held A1 certificates issued by the competent Spanish institution, confirming their affiliation to the Spanish social security system. 

Following inspections, the French social security collection body, URSSAF, identified evidence suggesting that the certificates had been obtained fraudulently. It asked the Spanish institution to review them and submitted concrete information in support of its request. 

The Spanish institution confirmed the certificates. However, the French courts considered that its response was superficial: it was not supported by documents capable of confirming its statements, did not address the evidence submitted by URSSAF and was not based on an effective investigation into the alleged fraud. 

The defendants argued that the French courts could not disregard certificates that the issuing institution had expressly maintained. 

A confirmation is not necessarily an effective review

The Court of Cassation distinguished between a formal confirmation and an effective review. 

The host State must first promptly initiate the dialogue and conciliation procedure and give the issuing institution a genuine opportunity to reconsider the basis on which the certificates were issued. This request must identify the concrete evidence suggesting that the certificates were obtained or relied on fraudulently. 

The issuing institution must then assess that evidence in accordance with its duty of sincere cooperation. A response that merely repeats general conclusions, without addressing the evidence, producing supporting material or carrying out the necessary investigation, may not qualify as an effective review. 

Where no effective review has taken place, the court of the host State may disregard the A1 certificates if it independently establishes the fraud, in accordance with the right to a fair trial. 

The finding of fraud requires both: 

• an objective element, showing that the conditions for obtaining or relying on the certificates were not met; and 

• a subjective element, showing an intention to circumvent those conditions in order to obtain the resulting advantage. 

A suspicion of fraud alone is therefore not sufficient. 

Referral to the Administrative Commission is optional 

The Court also clarified an important procedural issue. If the institutions of the two Member States disagree on the facts, referral to the Administrative Commission for the Coordination of Social Security Systems is optional. 

The host State institution's decision not to make such a referral does not prevent a national court from disregarding the certificates where the issuing institution failed to carry out an effective review. 

This should be distinguished from the initial dialogue between the competent institutions, which remains a mandatory preliminary step before a final finding of fraud in proceedings concerning undeclared work based on a failure to make social security declarations. 

The outcome of the case 

The Court of Cassation held that the Spanish institution's response did not demonstrate an effective review of the evidence submitted by URSSAF. The French Court of Appeal was therefore entitled to disregard the A1 certificates and to find that the fraud had been established. 

Although the judgment was partially quashed, this partial quashing concerned the scope of certain disqualifications from managing a business and the justification for the confiscation of certain property. It did not overturn the finding of guilt relating to the fraudulent A1 certificates, which became final. 

Practical implications for employers 

The decision does not reduce the A1 certificate to a simple administrative formality. It remains binding and continues to provide essential legal certainty in cross-border social security matters. 

However, employers should not assume that a confirmation from the issuing institution will, by itself, close a fraud inquiry in the host State. Where concerns are raised, the quality and traceability of the review will matter. 

Companies involved in postings or multi-state working arrangements should therefore: 

• verify that the factual conditions supporting each A1 application are satisfied and remain accurate; 

• retain evidence of the employer's activities in the sending State and of each worker's actual situation; 

• respond fully and consistently to requests from the competent institutions; 

• ensure that any review addresses the specific evidence raised by the host State; and 

• coordinate social security, employment law and criminal-risk analyses where allegations of undeclared work arise 

The judgment reinforces a balanced approach: mutual trust protects duly issued A1 certificates, but that trust requires genuine cooperation and an effective examination of concrete evidence when fraud is alleged. 

In France, particular attention is paid to A1 certificates and undeclared work in sectors such as construction, road transport, agriculture and the agri-food industry, but employers in all sectors should be able to substantiate the factual basis for their A1 certificates.

If you would like to understand how these changes apply to your organisation or personal situation, please get in touch with your local CELIA Alliance contact.