The mandatory rules that apply

Two rules that apply together.

The employment contract remains governed by the law of the home country, and it continues during the posting.

The employer must nonetheless observe the national rules classed as mandatory by the Luxembourg labour code.

These two propositions do not conflict: the contract keeps its governing law, but certain host-country rules bind its performance.

The mechanism is that of a mandatory floor, applying whatever the content of the home contract.

A firm cannot therefore invoke its national law to displace a Luxembourg mandatory rule.

Field	Applicable law	Effect on price
Employment contract	Home law, subject to exceptions	Indirect
Minimum wage and working time	Luxembourg law	Direct
Health and safety at work	Luxembourg law	Direct
Social security	Home law, under conditions	Indirect

Two main elements.

The employment contract itself, its formation, classification and termination.

The social security regime, the employee continuing in principle to be covered by the regime of the State where they habitually work, subject to the applicable coordination rules.

That social security continuity involves its own formalities, distinct from the posting declaration, to be checked with the competent institutions.

It is not presumed: a prolonged posting may change the affiliation.

The Luxembourg labour code classes certain provisions as mandatory. They apply whatever law the contract chooses.

Those provisions bind performance of the contract during the posting, irrespective of the law governing that contract.

They concern the working conditions applicable on the territory, in the fields the code designates.

This guide does not list those provisions, whose content derives from the labour code and is liable to change.

That list is to be checked with the competent administration, which publishes information for posting employers.

This point is decisive for pricing, as the next section shows.

This is the economic contribution of this article. These rules are priced in before the bid is submitted.

The working conditions applicable in the host country may differ from those of the home country.

A firm pricing its work on the basis of its usual costs may therefore underestimate the real cost of posting.

That gap is not a contingency: it follows from rules that can be known before pricing.

Checking the applicable mandatory rules is therefore part of building the price, on a par with travel or accommodation costs.

A firm discovering that gap after submitting its bid bears the difference, with no way of passing it on.

A point worth knowing.

The posting declaration includes the details of the direct subcontractor, which makes the chain visible to the administration.

Using subcontractors therefore does not dilute the obligations, as the article on subcontracting and its risks develops.

Four rules.

Check the mandatory rules before pricing, not after submitting the bid.

Do not transpose your usual costs without examining the conditions applicable on site.

Handle the social security formalities separately, distinct from the posting declaration.

Re-examine affiliation on a prolonged posting, continuity not being presumed.