Subcontracting obligations in Luxembourg

1. Scope — the parties in the subcontracting chain

The subcontracting obligations regime applies to any relationship in which a service provider entrusts all or part of the performance of a contract to a third party. The legal texts distinguish between several positions:

• The principal contractor (or client): the party contractually bound to the end client who relies on one or more subcontractors to perform its service;
• The direct subcontractor: the company that receives work directly from the principal contractor's contract. It is in relation to this party that the principal contractor's verification obligations are most extensive;
• Intermediate subcontractors: where a chain exists, liability may extend to any intermediate level that was aware of the irregularity.

The obligations described below apply regardless of the sector of activity, even though in practice the construction and civil engineering sectors concentrate the most frequent ITM inspections.

2. Employment of third-country nationals — verification and financial solidarity

Where the direct subcontractor employs third-country nationals (non-EU), the principal contractor is subject to a strict duty of vigilance regarding the regularity of their residence status and work authorisation.

Mandatory prior verification (Art. L.572-3)

The principal contractor must ensure that its direct subcontractor has carried out the following steps for each third-country national employed:

• required and verified the presentation of a valid residence permit or authorisation before hiring;
• retained a copy of that permit throughout the period of employment;
• notified the start of employment to the competent minister within the statutory time limits: 3 working days in general, 7 days for employment for private purposes (Art. L.572-3).

Financial solidarity in the event of irregular employment (Art. L.572-10)

If the direct subcontractor employs a national with irregular residence status, the principal contractor may be held jointly and severally liable, or solely liable, for:

• financial penalties imposed;
• wage arrears;
• unpaid social security contributions and taxes;
• costs of return to the country of origin.

In a subcontracting chain, liability may extend to any intermediate subcontractor who was aware of the worker's irregular residence status (Art. L.572-10, para. 2).

3. Social security — statutory solidarity for contributions

Luxembourg law establishes statutory joint and several liability by operation of law between the principal contractor and its subcontractors for all social obligations, without any need to establish fault or awareness of a breach.

General solidarity on employer obligations (Art. CSS-VI-444)

The principal contractor is jointly and severally liable with the subcontractor for fulfilling all obligations imposed on employers by the laws and regulations relating to social insurance. This solidarity covers all branches of Luxembourg's social security system (health, pension, accidents at work, long-term care).

Contributions and statutory benefits (Art. CSS-VI-431)

The principal contractor and subcontractors are jointly and severally liable for the payment of contributions and other statutory benefits owed to the Centre commun de la sécurité sociale (CCSS). The CCSS may therefore recover unpaid contributions from the subcontractor directly from the principal contractor.

4. Transnational posting — control of the ITM declaration

Where the direct subcontractor posts workers to Luxembourg under the contract entrusted to it, the principal contractor does not play a merely passive role: it takes on an active duty of control over the administrative regularity of the posting.

Verification of the prior declaration (Art. L.142-2, para. 2)

From the start of the posting, the principal contractor must ensure that its subcontractor has duly filed its declaration with the ITM via the dedicated electronic platform, in accordance with Art. L.142-2. This verification must be carried out before work begins: a missing declaration is an irregularity attributable to the subcontractor, but one whose absence the client cannot ignore.

Substitute declaration to the ITM (Art. L.142-2, para. 2)

If the subcontractor has not provided a copy of its declaration, the principal contractor must itself communicate the essential information to the ITM electronically, within eight days of the start of the posting. The information to be transmitted includes in particular the identity of the subcontractor and its posted workers, and the dates and location of performance.

5. Accommodation and health & safety

Duty to serve notice in the event of non-compliant accommodation (Art. L.291-2, para. 4)

Where the ITM notifies the principal contractor in writing that employees of its subcontractor are housed in conditions that do not meet habitability, hygiene and safety requirements, it must act in two stages:

1. Formally notify the subcontractor by recorded delivery letter to remedy the situation within eight days;
2. Inform the ITM if the subcontractor has not responded or has not remedied the situation within that period.

This duty of direct action distinguishes the accommodation area from other domains: the principal contractor cannot remain passive after notification by the ITM.

Health and safety at work — maintained liability (Art. L.312-1)

The principal contractor remains responsible for the safety and health of all workers on its sites, including those employed by its subcontractors. Engaging external providers or delegated prevention services does not relieve it of its risk prevention responsibilities. In practice, this means the principal contractor must integrate subcontractors' workers into its prevention plan and risk assessment.

6. Summary table of responsibilities