Where undeclared workers are used, the joint liability of the client and the parties hiring the workers is subject to a strict condition.
Pursuant to Article L. 8222-1 of the French Employment Code, if a party enters into any contract that relates to an obligation in consideration for a minimum amount for performance of a piece of work or that relates to the supply of services or to the carrying out of a legal transaction governed by commercial law, then that party is required check that certain steps have been taken by the other contracting party (notably regarding the risk of using undeclared workers) and such checks must be carried out periodically until the contract has been fully performed.
A failure to check that these steps have been carried out may have serious consequences insofar as a party simply disregarding them will become jointly liable in law, with the person who used the undeclared workers, for the payment of any levies, taxes, contributions, penalties and surtaxes and, if applicable, the payment of any remuneration, indemnities and charges. That party may also be jointly liable for the reimbursement of any sums that correspond to government aid.
However, in a landmark decision of 26 November 2015, the French Court of Cassation held that enforcement of such joint liability is conditional on an official report having been issued against the other contracting party for the offence of using undeclared workers.