Reform of the social security coordination regulations: Key changes

Within the European Economic Area (“EEA”), the determination of the applicable social security legislation is governed by Regulations (EC) No 883/2004 (“Basic Regulation”) and 987/2009 (“Implementing Regulation”). The fundamental principle remains that of the lex loci laboris: each employee is subject to the legislation of the State in which the activity is carried out. However, the regulations provide for specific rules to prevent a person from being subject to multiple social security systems in respect of the same employment:
 

• On the one hand, posting, which refers to the situation where an employee is temporarily sent by their employer to another Member State to perform activities of limited duration. In such cases, and subject to certain conditions, the employee may remain affiliated with the social security system of the sending State.
   
• On the other hand, the performance of activities in two or more Member States, or simultaneous employment. This covers employees who habitually carry out activities in several States, for example by alternating their working time between a State of residence and another State of employment. In this context, the determination of the applicable legislation is based on the notion of substantial activity.
   

On 23 April 2026, the Council of the European Union reached a provisional agreement on the reform of the basic and implementing regulations on the coordination of social security, based on the proposal put forward by the European Commission in 2016. This text was also approved by the European Parliament's Committee on Employment and Social Affairs on 6 May 2026.

It must still be formally adopted by the European Parliament in plenary before entering into force.

The reform covers several areas, including unemployment benefits, family benefits, and the rules on the applicable legislation for posted employees and people carrying out activities in several Member States.

This article focuses solely on the latter aspect, namely the rules governing the determination of the applicable social security legislation.

1. Strengthening of the conditions relating to posting

The posting regime, under which an employee is temporarily employed in another Member State, as set out in Article 12 of the Basic Regulation, constitutes a derogation from the lex loci laboris principle, allowing a posted employee to remain subject to the legislation of the sending State for a limited period, in principle set at 24 months. This principle is maintained under the reform.

However, the amendments introduced aim to significantly strengthen the conditions for applying this regime. This concerns in particular:
 

• “Chain posting” practices: While the current text already prohibits replacing one posted employee with another posted employee, the new wording explicitly extends this prohibition to situations involving self-employed persons.
   

The revised text nevertheless introduces an exception: a posted employee may replace another provided that the total duration of the successive assignments during which employees are successively posted does not exceed 24 months and that all other posting conditions are met (notably the normal performance of the employer’s activities in the sending State).

This development is in line with the Alpenrind judgment (C‑527/16), in which the Court of Justice adopted a broad interpretation of the concept of replacement, considering that it may be established even where the employees concerned are sent by different employers. While this interpretation is not called into question, the reform clarifies its scope and introduces an exception to avoid excessively rigid situations, notably where successive assignments form part of an overall time-limited framework.
 

• Strengthening of a genuine link with the social security system of the sending State: The current rules require that the employee be affiliated with this system “immediately before the start of his employment” in order to benefit from the continued application of the social security legislation of the sending State. Administrative practice stemming from Decision A2 of the Administrative Commission for the Coordination of Social Security Systems considers that this condition was fulfilled where the employee had been affiliated for at least one month prior to the posting. The reform introduces a minimum prior affiliation period — now set at three months — to ensure a genuine link and to prevent opportunistic short-term affiliations.
   

In the Walltopia judgment (C‑451/17), the Court of Justice had interpreted this requirement broadly, holding that mere residence in the sending State could suffice, even if the person was not insured under that State’s legislation. The new regulation seeks to neutralize this approach by replacing the requirement with a minimum three-month affiliation period, thereby reinforcing the genuine nature of the link with that Member State.
 

• Cooling-off period of 2 months: The reform codifies a rule previously stemming from administrative practice, notably Decision A2. It now provides that, following a posting period of 24 months, a break of two months must in principle be observed before a new posting to the same Member State can be initiated for the same employee (or self-employed person) (“cooling-off period”).

This requirement aims to prevent practices consisting of artificially chaining posting periods to unduly extend the application of the sending State’s social security system. It thus reinforces the coherence of the regime by imposing a genuine discontinuity between successive assignments.

This interruption period is not required, however, where the posting is extended beyond the 24-month period on the basis of a derogation agreement between Member States in accordance with Article 16 of the Basic Regulation. In such cases, the posting may be extended without resetting the clock, generally up to a maximum of five years.

2. Strengthening of information obligations and the A1 system

The Implementing Regulation provides that the employer or the employee informs, “whenever possible in advance”, the competent institution of the pursuit of an activity in another Member State. The reform seeks to turn this possibility into a genuine prior obligation, requiring systematic notification before the start of the cross-border activity.

At the same time, the role of the A1 certificate issued by the competent institution of the relevant Member State, which certifies the applicable legislation in cases of posting or simultaneous employment, is strengthened. The competent institution remains required, upon request of the interested party or the employer, to issue a document attesting to the applicable legislation, but the reform introduces an automatic acknowledgment mechanism where such certification cannot be issued immediately. This development is intended to provide legal certainty for cross-border situations from the outset of the assignment.

An exception is provided for very short assignments, limited to three days within a thirty-day period, outside the construction sector, reflecting an intention to reduce administrative burdens in low-risk situations.

3. Evolution of the binding effect of A1 forms

Article 5 of the Implementing Regulation establishes the principle that A1 forms issued by an institution of a Member State are binding on the institutions of other Member States as long as they have not been withdrawn or declared invalid. This rule has consistently been confirmed by the Court of Justice, notably in the A-Rosa (C‑620/15), Altun (C‑359/16), Alpenrind and DRV Intertrans (C‑410/21 and C‑661/21) judgments.

The reform does not formally amend this principle, as the mechanism for challenging certificates — based on dialogue between institutions and an obligation of sincere cooperation — already existed.

The reform builds on this framework by further clarifying and structuring its implementation, in particular through the introduction of more structured deadlines and mechanisms for resolving disagreements between institutions.

In practice, it thus strengthens the predictability and effectiveness of challenges to A1 certificates without altering their underlying principles.

4. Stricter framework for activities in several Member States

Finally, the reform introduces a stricter framework for situations involving activities in several Member States by strengthening the employee’s information obligations and formalizing the procedure for determining the applicable legislation (provisional decision followed by a definitive decision). 

It also introduces a time limit for such determinations, now capped at 24 months, requiring periodic reassessment of the ongoing situation in order to avoid the continuation of legal arrangements that no longer reflect the reality of the activity performed.

Conclusion

The reform marks a significant development in the European system for the coordination of social security. Without calling into question the fundamental principles laid down by Regulations 883/2004 and 987/2009 — foremost among them the lex loci laboris principle and the rule of a single applicable legislation — it considerably strengthens their implementation mechanisms.

It reflects a shift from a relatively flexible system largely based on mutual trust between Member States to a much more structured, procedural framework aimed at combating abuse.

The strengthened rules on posting, A1 forms, and information obligations clearly demonstrate a willingness to ensure a stricter and more transparent application of coordination rules, with direct implications for companies and internationally active employees.