A1 certificates and undeclared work: French Supreme Court clarifies when criminal courts may disregard an A1 certificate maintained by the issuing state
(French Supreme Court, Criminal Chamber, 9 June 2026, No. 24-85.090)
In a judgment handed down on 9 June 2026 and published in both the official Bulletin and Annual Report (No. K 24-85.090 FS-B), the Criminal Chamber of the French Supreme Court made a significant contribution to the body of case law governing intra-EU postings of workers and fraud involving A1 certificates.
The Court upheld most of a substantial conviction for undeclared work and unlawful labour supply by an organised group, issued by the Aix-en-Provence Court of Appeal, while partially overturning certain ancillary penalties.
Most importantly, the decision provides a detailed interpretation of European case law concerning the dialogue and conciliation procedure that must precede any decision to disregard an A1 certificate.
Background and procedural history
A labour supply company, initially established in Spain, carried out activities in France by providing workers to agricultural businesses. The company had obtained A1 certificates from the Spanish authorities, confirming that its posted employees remained affiliated with the Spanish social security system.
Beginning in 2011, investigations conducted by URSSAF and the French labour authorities revealed evidence suggesting fraud in the issuance of these certificates. URSSAF therefore requested that the competent Spanish institution review the certificates.
By letter dated 12 July 2017, the Spanish Ministry of Employment and Social Security refused to withdraw them, stating that the company carried out a substantial part of its activities in Spain and that the posted workers resided there. According to the Ministry, previous inspections by the Spanish labour inspectorate supported this position.
The company, together with several executives and employees, was subsequently prosecuted before the criminal courts for undeclared work (concealment of business activity and employees), unlawful labour supply by an organised group, and aiding and abetting those offences.
Convictions were issued at first instance on 8 July 2021 and subsequently confirmed on appeal by the Aix-en-Provence Court of Appeal on 12 June 2024. The penalties were particularly severe:
- a €500,000 fine and a permanent professional ban imposed on the company;
- prison sentences of up to four years, suspended, together with fines of up to €100,000 for certain executives;
- permanent professional bans imposed on all convicted individuals.
On the civil side, the defendants were held jointly liable for more than €80 million in unpaid social security contributions owed to URSSAF PACA, in addition to damages awarded to several other civil claimants, including ACOSS, trade unions and professional organisations.
Several appeals were lodged before the French Supreme Court.
The core issue: the legal effect of A1 certificates maintained by the issuing state
The European legal framework
The French Supreme Court first recalled the principle established by the Court of Justice of the European Union (CJEU).
Under the principles of sincere cooperation and mutual trust, an A1 certificate that has been duly issued creates a presumption that the worker is properly affiliated with the social security system of the issuing state. Such a certificate is binding on both the competent institutions and the courts of the host state unless and until it is withdrawn or declared invalid by the issuing authority.
(CJEU, 27 April 2017, A-Rosa Flussschiff, C-620/15; CJEU, 6 September 2018, Salzburger Gebietskrankenkasse, C-527/16).
However, this principle is subject to an exception based on the prohibition of fraud and abuse of rights, which constitutes a general principle of EU law.
In the landmark Ömer Altun judgment (CJEU, 6 February 2018, C-359/16), the CJEU held that where the institution of the host state requests the issuing institution to review and withdraw A1 certificates in light of evidence gathered during a judicial investigation demonstrating that the certificates were obtained or relied upon fraudulently, and where the issuing institution fails to take that evidence into account, the national court may disregard the certificates, provided that the existence of fraud is established while respecting the guarantees of a fair trial.
The CJEU further refined this approach in Vueling Airlines (CJEU, 2 April 2020, Joined Cases C-370/17 and C-37/18, paragraph 86). According to that judgment, courts of the host state may disregard A1 certificates only after verifying:
- that the dialogue and conciliation procedure was promptly initiated and genuinely enabled the issuing institution to reassess the validity of the certificates in light of the specific evidence submitted; and
- that the issuing institution failed to conduct such a review and to take a position within a reasonable period of time.
What constitutes an “effective review”?
The most significant aspect of the judgment concerns the assessment of the Spanish institution’s response.
The Court of Appeal had found that although the Spanish authorities replied to URSSAF’s request, their response was merely superficial and declaratory in nature. No investigation had been conducted by the Spanish labour inspectorate into the alleged fraud, despite indications that such action would be taken.
The French Supreme Court endorsed this reasoning and articulated a clear principle:
Where the institution of the issuing state confirms the validity of A1 certificates without addressing the specific evidence submitted by the host state and without conducting any investigation into that evidence, such a response cannot be regarded as an effective review.
n such circumstances, a court in the host state that establishes the existence of fraud may disregard the A1 certificates, notwithstanding their formal maintenance by the issuing state.
This clarification is particularly important in practice. It prevents an issuing state from indefinitely shielding A1 certificates through a purely formal response unsupported by documentary evidence or genuine investigative measures.
The French Supreme Court further indicated that it will itself review the documents exchanged during the dialogue and conciliation procedure to verify whether an effective review actually took place, demonstrating a willingness to exercise close scrutiny over this issue.
Referral to the Administrative Commission remains optional
The Court also addressed the question of whether the matter must be referred to the Administrative Commission for the Coordination of Social Security Systems in cases of disagreement between member states.
It held that such a referral remains optional under Regulation (EC) No. 883/2004.
Consequently, the decision of the host state institution not to refer the matter to the Administrative Commission does not deprive national courts of their authority to disregard A1 certificates where the issuing institution has failed to carry out an effective review.
No need for a preliminary reference to the CJEU
Finally, the Supreme Court rejected the argument that a preliminary reference should have been made to the CJEU.
The Court considered that the Altun and Vueling Airlines judgments already provide clear guidance regarding the circumstances in which courts of the host state may disregard A1 certificates.
Since there was no reasonable doubt as to the interpretation of the applicable EU law, no referral was required. This constitutes a conventional application of the acte clair doctrine.
Practical implications
From a social security and international posting perspective, the judgment reinforces a strict interpretation of the concept of an effective review established by the Vueling Airlines case law.
A response from the issuing state that is unsupported by documentary evidence and does not result from a genuine investigation will not prevent a French criminal court from disregarding A1 certificates, even where that response formally confirms their validity.
For companies relying on posted workers covered by A1 certificates, the decision highlights the importance of ensuring that, in the event of a challenge, the issuing state carries out a genuine and substantive examination of the case rather than merely issuing a formal confirmation of the certificates.
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