Letterbox companies

Companies which have complied only with the bare essentials (e.g., book-keeping, administration) for organisation and registration in a particular country. The actual commercial activities are often carried out in another country. This is sometimes used to enable businesses to deviate from applicable legislation, resulting in violations of labour law or collective agreements, tax and/or social security compliance, leading to undeclared or under-declared work.

[See also Directive 2014/67/EU of the European Parliament and of the Council of 15 May 2014 on the enforcement of Directive 96/71/EC concerning the posting of workers, article 4, para 2(b)]