European undertakings send, and will undoubtedly con­tinue to send, employees to other Member States in order to provide services to local entities. Such employees, tem­porarily assigned by their employers to work in another Member State, are referred to as posted workers. How­ever, the posting of workers is only ostensibly a matter as straightforward as a specific form of labour mobility whereby an undertaking, in exercising its freedom to pro­vide services, relies on employees engaged in one Mem­ber State to perform work in another. The issue becomes considerably more complex when one takes into account the interrelationship between the posting of workers and the institution commonly referred to as a “business trip”: a concept not recognised as such under EU law, albeit widely regulated and applied in the domestic legal systems of certain Member States. The primary objective of this study is to identify and analyse the legal challenges aris­ing in the field of workers’ mobility within the European Union. The analysis commences with an outline of the general legal framework established under EU law, with particular emphasis on the regime governing the posting of workers. Building upon the current state of the art, spe­cial attention is devoted to the conceptual and normative examination of the “business trip”, an institution absent from EU law and not uniformly recognised in the domes­tic laws of all Member States. In this context, the study examines national labour law provisions concerning “busi­ness trips” or analogous institutions in Bulgaria, the Czech Republic, Estonia, Latvia, Poland, Slovakia, and Slovenia.

Nowadays, employees more and more often undertake various types of business trips as part of their professional duties. A special category of such employees are the so-called mobile workers, i.e. workers moving within a strictly defined geographical territory. The purpose of the following study is to discuss the principles of reimbursement of accommodation costs incurred during business travel to mobile workers. The authors question the latest legislative changes to the principles of reimbursement of drivers' accommodation costs and the insufficient regulation of the principles of reimbursement of accommodation costs for other mobile workers and suggest intervention of legislator in that regard.

The purpose of the following study is to analyze the interdependence between the principle of sincere cooperation between the Member States of the European Union and the A1 certificate. First, the author analyzes the theoretical assumptions for the A1 certificate, especially in the context of the title principle. The document in question is not only a guarantor of fundamental freedoms, but also a sign of trust between the Member States. The author poses questions and considers numerous doubts regarding the issue of trust between the Member States, the limits of this trust and possible control measures, especially in the context of the abuse of treaty freedoms.