The conflict rules of European social security coordination in a digital labour market – bridging lex loci laboris and remote work by disregarding marginal cross-border activities

Abstract

The article explores the complexities of determining the social security legislation applicable to employees engaged in cross-border remote work under Title II of Regulation (EC) 883/2004. Using remote work as a case study, it analyses the systematic interplay of various conflict rules. Social security legislation is traditionally tied to the physical location of employment (lex loci laboris), but the rise of remote work disrupts this paradigm, potentially causing frequent shifts in applicable legislation whenever employees work from different Member States. This ‘ping-pong effect’ may undermine legal certainty, impose administrative burdens and jeopardise workers’ social security rights. The article critically evaluates the EU Administrative Commission's Guidance Note on telework, which promotes a flexible interpretation of exceptions under Articles 12, 13 and 16 of Regulation (EC) 883/2004. While these exceptions help to resolve some difficulties, the author argues that the Administrative Commission fails to address the fundamental issue: at what point does cross-border remote work trigger a change in jurisdiction under the main rule in Article 11(3)(a)? The findings suggest that marginal activities – defined as constituting less than 5% of total working time and/or remuneration – should be disregarded within simultaneous and alternating working patterns under lex loci laboris. Such an approach allows the ‘usual’ State of employment to retain jurisdiction, thereby ensuring continuous affiliation for workers. Exclusion of de minimis activities is presented as a proportionate outcome, supported by the fundamental freedoms of free movement in primary EU law.

Introduction

This article examines the social security legislation applicable to employees working remotely across borders within the internal market. Using remote work as a case study, it aims to analyse how different conflict rules interact on a systematic level. The key message is that these rules accommodate a certain degree of worker mobility, enabling short-term cross-border remote work without triggering changes in the applicable legislation. ¹

Regulation (EC) 883/2004 establishes a system of coordination, concerning in particular the determination of the legislation applicable to workers who exercise their right to freedom of movement. ² Article 11(3)(a) states that, as a general rule, workers shall be subject to the legislation of their State of employment (lex loci laboris). ³ This is traditionally the Member State in which the work is physically performed.

Remote work, however, challenges the concept of a physical workplace. Regulation (EC) 883/2004 must be interpreted in light of Article 48 TFEU, which seeks to help establish the greatest possible freedom of movement. ⁴ Frequent changes in applicable legislation each time employees work remotely from another Member State could hinder free movement and jeopardise their entitlement to benefits, due to brief interruptions in affiliation.

On 21 June 2023, the EU Administrative Commission for the Coordination of Social Security Systems issued a new Guidance Note on telework, advocating a more flexible interpretation of the existing legal framework (Administrative Commission, 2023: 2). While reaffirming that exceptions to general rules should, in principle, be interpreted restrictively, Member States were encouraged to apply the exceptions in Articles 12 and 13 of Regulation (EC) 883/2004 more broadly and, where necessary, to derogate from Article 11(3)(a) by mutual agreement under Article 16(1).

Although the Guidance Note enhances legal certainty for remote workers, it leaves a critical issue unresolved: at what point does cross-border remote work trigger a change in applicable legislation under lex loci laboris? The exceptions to Article 11(3)(a) were designed for longer-term activities and entail procedural requirements that seem cumbersome and disproportionate for short-term remote work arrangements.

I argue that marginal cross-border activities ⁵ within simultaneous ⁶ and alternating ⁷ working patterns should be disregarded under lex loci laboris. Such an approach allows the worker's ‘usual’ State of employment to retain jurisdiction, thereby ensuring continuous social security affiliation. This interpretation aligns with the wording of Article 11(3)(a) and is supported by the purpose, good policy reasons and the fundamental freedoms of movement in primary EU law.

The article is structured as follows: the next section discusses the challenges of applying lex loci laboris to remote work. The Guidance Note and its proposed interpretations are then presented. The subsequent section examines the possibility of disregarding marginal activities under lex loci laboris. The final part brings everything together and illustrates the broader implications of the findings.

Lex loci laboris and remote work

Since its inception in the 1950s, lex loci laboris (the law of the place of work) has been a cornerstone of European social security coordination. ⁸ As observed by the Administrative Commission (2023: 3), this principle traditionally designates the Member State in which the work is physically performed. The seminal ruling is the Partena judgment, which involved a director managing a Belgian company from his residence in Portugal. The ECJ held that the ‘location’ of an activity is a concept of EU law that refers to ‘the place where, in practical terms, the person concerned carries out the actions connected with that activity’. ⁹

Scholars have warned that remote work ‘allows people to work swiftly from different places (in different countries) or to have the work organised in such a manner that it is located in countries with low-cost systems of social security’ (Strban et al., 2020: 15–16, see also Bermejo, 2023; Jorens et al., 2008: 5; Lhernould, 2023; Rennuy, 2017: 424–425; Schoukens, 2020: 442; Verschueren, 2022). In theory, the physical workplace concept under lex loci laboris could result in the applicable legislation repeatedly changing back and forth as work is performed remotely across different Member States. Such a ‘ping-pong effect’ risks undermining the objectives of Regulation (EC) 883/2004. ¹⁰

First, frequent changes in applicable legislation would threaten the legal certainty crucial to European social security coordination. The sole objective of Regulation (EC) 883/2004 is to ensure the coordination of national social security schemes to guarantee the effective exercise of the freedom of movement of persons. ¹¹ This implies that migrant workers must not lose their right to social security benefits or have the amount of those benefits reduced because they have exercised their right to free movement. ¹² Since primary EU law cannot guarantee that moving to another Member State will be neutral in terms of social security, ¹³ the coordination rules presume that individuals make informed decisions (Pennings, 2022: 4).

Second, requiring workers to affiliate with another Member State for short periods would impose significant administrative burdens on employers and authorities, potentially hindering free movement. ¹⁴ Frequent changes might also lead to bigger discrepancies in applicable frameworks for social security, labour law and taxation, making compliance even more difficult (for details, see Lhernould et al., 2017; Spiegel et al., 2022).

Third, workers may lose entitlement to benefits due to brief interruptions in affiliation. ¹⁵ Although Member States must take into account insurance periods completed under the legislation of other Member States, ¹⁶ the principle of aggregation does not fill in all the gaps. For instance, Member States are not required to provide invalidity or old-age benefits for insurance periods of less than one year, although these must be included in the calculation of pro rata benefits. ¹⁷ Even if other provisions mitigate the most severe effects, workers may find themselves ineligible for benefits from Member States, and receive reduced benefits from others (see also Lhernould, 2015: 460; Schoukens and Pieters, 2009: 106–107; Van Ooij, 2023: 257–258).

Legal scholarship has discussed specific connecting factors tailored to remote work (e.g. Bermejo, 2022, 2023; Jorens et al., 2008: 5; Lhernould, 2015: 459). One proposed solution is the concept of a ‘virtual workplace’, where the location of the employer serves as the connecting factor. While this proposal deserves consideration by lawmakers, its interpretation under Article 11(3)(a) raises challenges.

The physical workplace concept is a strong starting point. The objective of lex loci laboris is to guarantee equality of treatment of all persons occupied in the territory of a Member State as effectively as possible. ¹⁸ By preventing divergent rules for migrant workers and maintaining a level playing field in the host State, lex loci laboris is in principle required under free movement ¹⁹ and protects against social dumping. ²⁰ A focus on the actual State of employment strikes a better balance between free movement and fair competition than using the employee's State of residence or the employer's State of establishment (e.g. Rennuy, 2021). Given the diverse nature of remote work – including home office set-ups, workcations, platform work and digital nomadism – it remains uncertain whether a one-size-fits-all solution is feasible, thus necessitating careful consideration in legislative processes.

Furthermore, singling out the case of remote work by arguing that the Partena judgment concerned a self-employed person (e.g. Bermejo, 2022: 227–230, 2023: 84–86) is not straightforward. At the heart of Regulation (EC) 883/2004 lies the single-state principle enshrined in Article 11(1), which stipulates that persons covered by that regulation should be subject to the legislation of a single Member State only. Its objective is twofold: to prevent the simultaneous application of multiple national legislative systems and the complications that this might entail, and to ensure that persons are not left without social security cover because there is no legislation which is applicable to them. ²¹ To that end, Article 11(3)(a) makes a person pursuing employment ‘in a Member State’ subject to the legislation of ‘that Member State’ in a circular manner. When read in conjunction with Article 1(a), which defines ‘activity as an employed person’ as ‘any activity or equivalent situation treated as such for the purposes of the social security legislation of the Member State in which such activity or equivalent situation exists’, lex loci laboris implies a three-step assessment for determining the legislation applicable:

Identify the Member State in which the activity exists;

Determine whether the legislation of that Member State classifies the activity as employment or self-employment; and

If classified as employment or self-employment, assign jurisdiction to that Member State as the State of employment under lex loci laboris.

This reveals an inherent conflict within the conflict problem itself: which legislation should define the activity in question? ²² In the Partena judgment, the ECJ made a double choice (see also Rennuy, 2017: 365–367): while the concepts of ‘employment’ and ‘self-employment’, in terms of their content, fall under the legislation of the Member States, the location of an activity is a concept of EU law. ²³ The Court reasoned that if the location was also a matter for national legislation, it could be subject to contradictory definitions and lead to the cumulative application of different legislations to the same activity, which would be manifestly contrary to the objectives pursued. ²⁴ Consequently, since the location of an activity must be determined before its content, interpreting specific connecting factors for various activities, such as remote work, is difficult.

The Administrative Commission's (2023: 3) physical approach to the workplace – effectively equating remote work with conventional cross-border work under lex loci laboris – is therefore sound. This does not mean we should call off the search for better solutions de lege ferenda, but a proper understanding of the existing legal framework is essential for such endeavours. Valid concerns about employers exploiting remote workers from low-cost Member States should be tackled by specific rules at the European or national level, rather than by altering the key principles of coordination. ²⁵ The risk of a ping-pong effect is also not unique to remote work. It is settled case law that the unrestricted application of lex loci laboris might create, rather than prevent, administrative complications for workers as well as for employers and authorities, which could impede free movement. ²⁶ As stated in Article 11(3), the main rule is therefore ‘[s]ubject to Articles 12 to 16’. ²⁷ The following sections will examine whether the Administrative Commission's interpretations can effectively address the challenges posed by applying lex loci laboris to remote work arrangements.

Interpretations in the Guidance Note

Scope and legal significance

The Guidance Note on telework was adopted by the Administrative Commission on 21 June 2023. This body is composed of government representatives from the Member States, with the European Commission participating in an advisory role. ²⁸ Its main task is to foster cooperation by addressing all administrative and interpretative questions, thereby facilitating the uniform application of EU law. ²⁹

Article 72(a) of Regulation (EC) 883/2004 stipulates that measures adopted by the Administrative Commission are ‘without prejudice to the right of the authorities, institutions and persons concerned to have recourse to the procedures and tribunals provided for by the legislation of the Member States, by this Regulation or by the Treaty’. Although the Guidance Note is not legally enforceable, it reflects a consensus among the majority of Member States and serves as a useful tool for national institutions (Bermejo, 2023: 62–63; Van Ooij, 2022: 48–49). ³⁰

The interpretations set out in the Guidance Note were developed in response to the challenges posed by COVID-19. During the pandemic, the Administrative Commission recommended that, due to force majeure, the applicable legislation should remain unchanged for workers obliged to perform cross-border telework by containment measures (Administrative Commission, 2023: 1; for details, see Verschueren, 2022). ³¹ As telework would remain a way of working, it became necessary to assess the application of the current legal framework in normal circumstances. Recognising that these new interpretations could lead to different results, the Administrative Commission introduced a one-year transition period. The updated Guidance Note, applicable from 1 July 2023, replaces its predecessor (Administrative Commission, 2022), with only minor amendments.

As of 1 January 2025, 22 States have also entered into a Framework Agreement on the application of Article 16(1) in cases of habitual cross-border telework (for details, see Lhernould, 2023: 27–29). ³² In contrast to the non-binding nature of the Guidance Note, the Framework Agreement imposes legally binding provisions on its signatories. It essentially allows teleworkers, subject to specific conditions, to remain subject to the legislation of their employer's State of establishment. ³³

The scope of both the Guidance Note and the Framework Agreement is explicitly limited to telework, defined as work involving the use of information technology to connect employees to their employer's working environment. ³⁴ This definition covers the most common forms of remote work in practice. ³⁵ Moreover, the interpretations in the Guidance Note are firmly grounded in the broader context and purpose of Regulation (EC) 883/2004 and may apply by analogy to other forms of remote work beyond their explicit scope.

The posting rule

Having emphasised the importance of the physical workplace under lex loci laboris, the Administrative Commission (2023: 3–5) introduces the posting rule as the first exception. Article 12(1) of Regulation (EC) 883/2004 allows employers to temporarily assign workers to another Member State while maintaining affiliation with the home State where the employer is established. Unlike the single criterion under lex loci laboris, the posting rule requires compliance with several cumulative conditions, as outlined in legal scholarship (e.g. De Wispelaere and Vukorepa, 2023: 233–234; Jorens, 2022: 294–316; Pennings, 2022: 120):

The employee must be subject to the legislation of the home State at the time of posting;

The employee must perform work on that employer's behalf;

The employer must normally carry out activities in the home State;

The posting period cannot be expected to exceed 24 months; and

The employee cannot be posted to replace another posted person.

Most of these conditions pose no greater challenges for remote work than for conventional work. While Bermejo (2022: 237, 2023: 77) suggests that determining the duration of remote work might be difficult, this appears to be more of a practical challenge than a matter of interpretation. Article 12(1) refers to the ‘anticipated duration’ of such work. If it is clear from the beginning that the remote work arrangement will exceed 24 months, the posting rule is inapplicable. Should this become clear only during the posting period, the worker will become subject to the legislation of the host State under lex loci laboris upon its expiration (Jorens, 2022: 311–312; Pennings, 2022: 127). Where the issue arises after the worker has returned to the home State – arguably the most common remote work scenario – it simply involves establishing a timeline, which both the employee and employer share an interest in clarifying.

Bermejo (2022: 237, 2023: 77) further argues that the prohibition on replacement may become irrelevant. Although remote work rarely involves the replacement of posted workers, this does not deprive that condition of useful effect. Together with the time limit, it ensures the temporary nature of postings. The territorial equality objective of lex loci laboris would otherwise require a change in applicable legislation (Rennuy, 2017: 389–390).

The main challenge in applying the posting rule to remote work revolves, rather, around the concept of ‘posting’ itself. Article 12(1) stipulates that the worker must be posted by the employer to another Member State to work on the employer's behalf. At the heart of the posting rule lies the provision of cross-border services, where workers are sent abroad to perform specific tasks. ³⁶ Remote work, often initiated by the employee without ties to any service, challenges the traditional understanding of posting. ³⁷

According to the Administrative Commission (2023: 3–4), however, the posting rule is applicable to any telework agreed upon (formally or informally) between the employer and the employee. ³⁸ This interpretation is well-founded. The wording requires some sort of involvement from the employer but does not specify its form. Provided the worker remains under the employer's authority, ³⁹ the decisive factor should be whether the employer, in some capacity, has authorised the employee to work abroad. The application of the posting rule thus appears straightforward when employers initiate remote work arrangements, and conversely, it is excluded when employers have no reason to know that their employees are working remotely from another Member State (Verschueren, 2022: 86, but see Bermejo, 2022: 236).

Between these extremes, the application of Article 12(1) of Regulation (EC) 883/2004 boils down to the specifics of each case. It is settled case law that the conflict rules depend on the worker's objective situation. ⁴⁰ In line with Article 14 of Regulation (EC) 987/2009 on related matters, an overall assessment should be made of all relevant facts, including the employment contract, collective agreements and past practices. Consideration must also be given to the nature of the employment relationship and the level of autonomy afforded to the employee. It is typically the employer's responsibility, within the framework of the employment contract, to organise, supervise, allocate and oversee the work. Tacit approval may therefore be inferred in situations where employees are permitted to work remotely from any location.

On the one hand, it could be argued that applying Article 12(1) of Regulation (EC) 883/2004 to employee-initiated remote work involves an overly broad interpretation of the phrase ‘posted by that employer to another Member State’. As an exception to a general rule, this provision should, in principle, be interpreted narrowly. ⁴¹ If the employer is required neither to initiate nor to specifically approve the remote work from another Member State, Article 12(1) could instead be framed as encompassing anyone ‘working for that employer in another Member State’. Furthermore, Article 15(1) of Regulation (EC) 987/2009 presumes that employers usually are directly involved by obliging them to inform, whenever possible in advance, the competent institution of the home State about the posting, ⁴² which in turn shall inform the host State of the applicable legislation. ⁴³

On the other hand, the objectives of Regulation (EC) 883/2004 clearly suggest a broader interpretation. The posting rule seeks to promote free movement and encourage economic interpenetration by preventing the applicable legislation from changing under Article 11(3)(a). ⁴⁴ Frequent changes impose significant administrative burdens on workers, employers and authorities alike. Since remote work primarily impacts the home State's market where the employer is established, and concerns about maintaining fair competition in the host State are consequently less pressing, the territorial equality objective of lex loci laboris does not require a change in applicable legislation.

In conclusion, while the posting rule may apply to remote work, it does not resolve all issues. If employers are unaware of work being performed abroad, workers may fall outside the scope of Article 12(1) of Regulation (EC) 883/2004, potentially triggering a change in applicable legislation under lex loci laboris. Furthermore, the administrative procedures connected with posting seem disproportionate, given the sporadic and temporary nature of many remote work arrangements (see also De Wispelaere and Vukorepa, 2023: 238).

The multi-activity rule

The Administrative Commission (2023: 5–6) refers to the multi-activity rule as the second exception to lex loci laboris. According to Article 13(1) of Regulation (EC) 883/2004, persons who ‘normally’ pursue an activity as an employed person in two or more Member States are subject to the legislation of either their State of residence or their employer's State of establishment. ⁴⁵ By covering individuals who work simultaneously or in alternation in two or more Member States ⁴⁶ and consolidating all their activities within a single Member State, ⁴⁷ the multi-activity rule embodies the single-state principle and underscores the importance of continuous affiliation. ⁴⁸

Remote work does not raise specific questions concerning the interpretation of Article 13 of Regulation (EC) 883/2004. Jorens (2022: 331) seems to suggest that remote work must be agreed upon in advance for the multi-activity rule to apply, but such a requirement cannot be inferred from its wording. It is settled case law that the multi-activity rule applies to any worker who ‘habitually carries out significant activities’ in the territory of several Member States. ⁴⁹ As observed by the Administrative Commission (2023: 5), this necessitates an overall assessment, in particular concerning the duration of periods of activity, the nature of the employment as defined in the contractual documents, and the actual work performed. ⁵⁰ Under Article 16 of Regulation (EC) 987/2009, workers may request that their State of residence determines the legislation applicable. This provisional determination becomes effective within two months of informing other Member States unless objections are made. For prospective assessments, national authorities consider the situation projected for the following 12 calendar months, ⁵¹ whereas retrospective assessments consider the actual work performed within each Member State. ⁵² Therefore, when employees spend a considerable amount of time working remotely across borders – such as 20% (one day per week) – the conditions for multi-activity are generally met, even without prior agreement.

The core issue rather lies in distinguishing between multi-activity and posting. Article 14(7) of Regulation (EC) 987/2009 clarifies that the duration of the activity in one or more Member States – whether permanent, ad hoc, or temporary – is decisive. Case law further refines this distinction by specifying that while a worker must ‘habitually carry out significant activities’ across multiple Member States, the work performed in one Member State's territory cannot constitute the worker's ‘normal arrangement’. ⁵³ Consequently, work performed remotely from another Member State must demonstrate both a degree of significance and regularity, without overshadowing the work physically performed at the employer's premises. Occasional and temporary cross-border remote work hence falls under the posting rule, while remote work that forms part of a fixed and regular routine is subject to the multi-activity rule. ⁵⁴

If the substantive conditions for multi-activity are met, Article 13(1) of Regulation (EC) 883/2004 outlines five conflict rules. The primary principle is lex loci domicilii, provided that a ‘substantial part’ of the activities is carried out in the State of residence. ⁵⁵ This is subject to a quantitative assessment based on working time and/or remuneration, with a share of less than 25% indicating that a substantial part is not carried out in the relevant Member State. ⁵⁶ Under the Framework Agreement, however, habitual teleworkers may request to remain subject to the legislation of their employer's State of establishment, provided that telework in the State of residence constitutes less than 50% of their total working time.

In conclusion, the multi-activity rule does not resolve all remaining issues related to remote work. Occasional and temporary cross-border remote work falls outside its scope, excluding, in practice, various significant remote work arrangements. Furthermore, the administrative procedures are more extensive than those for posting, requiring coordination among all Member States in which remote work is performed.

The derogation clause

The Administrative Commission (2023: 6–7) refers to the derogation clause as the ultimate exception to lex loci laboris. Article 16(1) of Regulation (EC) 883/2004 empowers Member States, by common agreement, to provide for exceptions to all previous provisions of Title II. Its objective is to serve as a safety net when the general conflict rules result in undesirable outcomes (Essers and Pennings, 2020: 165; Jorens, 2022: 363; Steinmeyer, 2015: 189; Van Ooij, 2022: 132). Member States enjoy a wide discretion to which the only limitation is regard for the interests of the worker. ⁵⁷ Such agreements may involve ‘[t]wo or more Member States’, apply to ‘certain persons or categories of persons’, and cover both future and retrospective periods. ⁵⁸

The Framework Agreement on telework is a notable innovation. Article 3 stipulates that persons who carry out habitual cross-border telework will, upon request, be subject to the legislation of the State in which their employer has its registered office or place of business, provided that telework in the State of residence constitutes less than 50% of their total working time. By essentially streamlining the procedure under Article 16(1) of Regulation (EC) 883/2004, the Framework Agreement seeks to eliminate the need for case-by-case assessments. Once the conditions are verified, workers who submit a request automatically qualify for exemption. This initiates the formation of an individual agreement between the employee's State of residence and the employer's State of establishment, ⁵⁹ provided that both Member States are signatories to the Framework Agreement. ⁶⁰

Despite the possibility for Member States to negotiate exceptions to accommodate remote workers, the Administrative Commission's (2023: 6) reliance on Article 16(1) of Regulation (EC) 883/2004 as ‘the tool to address the new/atypical work situations in all other cases’ is nevertheless unsatisfactory. Unlike Articles 12 and 13, workers cannot compel authorities to enter into such agreements. Although principles of loyalty and mutual trust may, in exceptional cases, require Member States to find adequate solutions to facilitate free movement, ⁶¹ it ultimately falls to national authorities to determine the appropriate measures. The derogation clause is thus only one of several options and the time required to conclude such agreements often extends beyond the commencement of cross-border remote work, leaving workers in a state of uncertainty. The core issue of how to interpret the conflict rules to ensure that freedom of movement for remote workers becomes effective thus persists.

Short-term remote work arrangements

The issue

Following the path set out by the Administrative Commission, this article has thus far sought to bridge the gap between lex loci laboris and cross-border remote work by interpreting Articles 12, 13 and 16 of Regulation (EC) 883/2004 broadly. These provisions, however, do not always prevent changes in the applicable legislation and are designed for longer-term cross-border activities, involving procedural requirements that seem cumbersome and disproportionate in the context of temporary remote work. The main problem with such an approach is its apparent recognition of only three distinct classifications for determining the legislation applicable to cross-border remote work under the general conflict rules:

Temporary posting under Article 12;

Regular multi-activity under Article 13; or

Successive application of Article 11(3)(a).

The third possibility involves a specific interpretation of lex loci laboris, under which the applicable legislation changes each time an employee performs remote work in a different Member State. This leaves workers with no choice but to seek recourse to an Article 16 agreement, thereby placing them at the discretion of national authorities and in a state of legal uncertainty.

This section challenges the presumption of territorial immediacy and argues for a more nuanced interpretation of Article 11(3)(a) of Regulation (EC) 883/2004. Consider the following scenario: an employee works remotely from State B on a Friday for an employer based in State A and remains there over the weekend. If this remote work arrangement is a one-time, unplanned event, neither the posting rule nor the multi-activity rule appears applicable. Should the applicable legislation really shift from State A to State B on Friday, only to revert on Monday? Or is there a legal basis for disregarding the remote work performed in State B and continuing to apply the legislation of State A for the entire period?

Leaving it to the Member States?

One possible solution is to leave this issue to the Member States. Some might even question its practical relevance, arguing that the risk of a ping-pong effect is largely hypothetical. Host States may be unaware of an employee working remotely within their territory and be reluctant to apply their legislation due to administrative complications. Furthermore, since the concept of ‘activity as an employed person’ is defined by national law, ⁶² short-term remote work may not even qualify as such under the host State's legislation. If a host State does insist on enforcing its laws, the coordinative framework provides mechanisms for resolving disputes with the home State.

In my view, however, leaving this issue to the discretion of Member States is inadequate. While some Member States may disregard temporary remote work, such an approach cannot be uniformly applied across the EU. Social security affiliation typically depends on the substantive nature of the employment relationship. ⁶³ Even brief periods of work conducted in the territory of a host State may trigger the application of its legislation, as demonstrated by the prevalence of short-term postings related to business travel. ⁶⁴

The legal uncertainties surrounding temporary cross-border remote work merit careful consideration. Appropriate information on all essential aspects of remote work is necessary to enable workers to exercise their right to free movement in practice and for authorities to fulfil their obligations to provide guidance (for details, see Berki, 2018: 179–199). ⁶⁵ As Jorens (2022: 235) aptly notes: ‘The problem with the principle of lex loci laboris is, however, that this principle is very volatile. From the moment the person concerned starts to work in another Member State, the lex loci laboris principle will immediately lead to a change of applicable legislation.’ Verschueren (2022: 86, see also De Wispelaere and Vukorepa, 2023: 241–242) further argues that ‘[i]f the posting rule does not apply, then the State of employment principle has to be applied so that the worker is subject to the legislation of the Member State in which they actually work, even if it concerns a short period’. Although no one likely intends for a ping-pong effect to occur, the common portrayal of lex loci laboris may conceal nuances. Taken to its logical extreme, even minor work tasks performed abroad will trigger changes in applicable legislation.

Ultimately, Title II of Regulation (EC) 883/2004 constitutes a complete and uniform system of conflict rules. ⁶⁶ These rules are mandatory for Member States, precluding them from unilaterally deciding the extent to which their own legislation or that of another Member State applies. ⁶⁷ While employers and national authorities may often ignore marginal cross-border activities, such practices require a valid legal justification.

Disregarding marginal cross-border activities

As an alternative, I submit that, in order to uphold the single-state principle and attain the objectives pursued, European social security coordination requires a clear delineation of when jurisdiction shifts from one Member State to another. ⁶⁸ The allocation of jurisdiction is subject to an interpretation of Article 11(3)(a) of Regulation (EC) 883/2004.

First of all, the wording of Article 11(3)(a) of Regulation (EC) 883/2004 is ambiguous, as the reference to the Member State in which the worker is ‘pursuing’ employment is open to interpretation. This wording could be understood to refer either to the physical location where the work is performed or to the Member State with the closest connection to the employment relationship. Since a literal interpretation does not provide definitive guidance, it is necessary to interpret the provision in light of its context and the objectives of Regulation (EC) 883/2004 as a whole. ⁶⁹

The context of Article 11(3)(a) of Regulation (EC) 883/2004 suggests a distinction between the actual work performed and the employment relationship itself. The conflict rules give effect to the single-state principle ⁷⁰ by determining the Member State to which EU citizens are most closely connected and to whose legislation they are therefore subject. ⁷¹ Settled case law confirms that lex loci laboris revolves around the existence of an employment relationship, ⁷² making workers subject to the legislation of their State of employment even when they are not actually working, such as during periods of leisure. ⁷³ Article 12(1) reinforces this distinction, referring separately to the ongoing direct relationship with the employer established in the home State and the work performed in the host State. The connecting factor under lex loci laboris therefore pertains to the legal construct of the employment relationship and should not be interpreted in a purely immediate or physical sense.

Nevertheless, while the physical presence of the worker at any given time cannot be conclusive under Article 11(3)(a) of Regulation (EC) 883/2004, the Partena judgment makes it clear that it cannot be entirely disregarded. ⁷⁴ The conflict rules depend not on the free choice of employees, employers or national authorities, but on the objective situation of the worker concerned. ⁷⁵ Since their application is not confined to the wording of contractual documents, the critical question is when a worker's activities in another Member State are sufficient to warrant reclassifying the employment relationship as having been ‘transferred’ to that Member State.

From a temporal point of view, a combined reading of Article 11(3)(a) of Regulation (EC) 883/2004 with Article 13(1) – which refers to an individual who ‘pursues an activity as an employed person in two or more Member States’ – suggests that if a cross-border activity does not initially meet the threshold for multi-activity during a given period, the worker should not be considered as pursuing employment in ‘two or more Member States’ but rather in one. Following this line of argument, Article 11(3)(a), read in conjunction with the single-state principle under Article 11(1), indicates that a single workplace should be identified for the relevant period.

Such an interpretation, logically stemming from the system of Title II of Regulation (EC) 883/2004, has the effect of excluding certain marginal activities from lex loci laboris. According to Article 14(5b) of Regulation (EC) 987/2009, marginal activities shall be disregarded under Article 13 of Regulation (EC) 883/2004. In keeping with previous case law, ⁷⁶ the Administrative Commission (2013: 27) defines marginal activities as ‘permanent but insignificant in terms of time and economic return’ and suggests a threshold of 5% for both working time and remuneration. This definition also considers the nature of the activity – whether it is supportive, dependent, conducted from home, or aimed at maintaining the main activity. While a strict reading of Article 14(5b) of Regulation (EC) 987/2009 might suggest that the exception for marginal activities only applies to cases of multi-activity, and not to other conflict rules, ⁷⁷ the multi-activity rule as such remains relevant in a contextual interpretation of lex loci laboris, suggesting that a similar exception could be inferred under Article 11(3)(a) of Regulation (EC) 883/2004.

The logic of a single workplace is particularly appropriate in the context of simultaneous working patterns, for instance workers with marginal secondary employment alongside their primary job. Regulation (EU) 465/2012 amended Article 14(5) of Regulation (EC) 987/2009, with a dual objective: to simplify the existing provision by removing the distinction between ‘simultaneous’ or ‘alternating’ activities, thereby enhancing legal certainty for persons pursuing an effective and genuine activity in one Member State and in parallel only a marginal activity in another, and to avoid possible misuse (for details see Van Ooij, 2022: 48). ⁷⁸ Consequently, by disregarding marginal side activities, only the primary activity is considered under lex loci laboris in the context of simultaneous working patterns. The objective of simplification suggests, a fortiori, that alternating working patterns – where employees successively work for the same employer across different Member States – should be treated similarly.

This contextual interpretation is further supported by the purpose of Article 11(3)(a) of Regulation (EC) 883/2004 and the objectives of European social security coordination. As the ECJ held in one of its first rulings in this field, ‘the aim of the regulation is to avoid any plurality or purposeless confusion of contributions and liabilities which would result from the simultaneous or alternate application of several legislative systems’. ⁷⁹ A paradox would come into being if marginal activities were excluded under the multi-activity rule yet included under lex loci laboris, thereby creating a problematic ping-pong effect. The territorial equality objective underpinning lex loci laboris does not call for a different interpretation, as the actions connected with that employment are predominantly carried out in the ‘usual’ State of employment.

Finally, to disregard marginal cross-border acitivities within alternating working patterns would not be a novelty in case law. The logic of a single workplace for a given period under lex loci laboris was already evident in the Hakenberg judgment, prior to the introduction of the multi-activity rule. ⁸⁰ The case concerned the determination of the legislation applicable to a representative of various French industrial companies who sold mechanical products to German manufacturers and wholesalers. Over the course of a year, he spent approximately nine months on sales trips in Germany while regularly returning to France to maintain client contact, for a total of about three months.

The Court observed that lex loci laboris operates on the presumption that a worker’s employment is normally confined to the territory of a single Member State. ⁸¹ In order to safeguard the single-state principle, the features of the activity had to be analysed to establish whether it had a predominant connection with the territory of one or other of the Member States concerned, requiring consideration not only of the duration of periods of activity but also of the nature of the employment in question. ⁸² Ultimately, while Mr Hakenberg was found to have been employed in the territories of both Member States, the predominant place of employment for the purpose of determining the applicable legislation was held to be the Member State in which the registered offices of the undertakings he represented were located. ⁸³

While Hakenberg is an exceptional case – one that would fall within the scope of the multi-activity rule under the current legal framework – there is no indication that either the EU legislature or the ECJ intended to overturn the fundamental presumption under lex loci laboris that a worker is generally deemed to be employed within a single Member State. The Partena judgment – the ‘founding precedent’ of the presumption of territorial immediacy – involved a person who primarily worked from his State of residence, and does not preclude a pragmatic approach to Article 11(3)(a) of Regulation (EC) 883/2004, consistent with its context and purpose. ⁸⁴

In my view, the logic of a single workplace under lex loci laboris in cases falling outside the scope of the multi-activity rule was reaffirmed by the ECJ in the X judgment of 2017. ⁸⁵ Although that judgment was rendered under Regulation (EEC) 1408/71, it remains relevant under Regulation (EC) 883/2004, which modernised and simplified the rules of its predecessor while retaining the same objective. ⁸⁶ A closer analysis reveals that the judgment not only clarifies the scope of the multi-activity rule but also, more fundamentally, its interaction with lex loci laboris.

The case concerned the determination of which Member State a frontier worker (referred to as X) should pay social security contributions to. In the course of the year, X had worked 121 h from his residence in Belgium, constituting 6.5% of his total working time. These activities were neither conducted in a regular pattern nor foreseen in his employment contract. X argued that the conditions for multi-activity were met, thereby making him subject to the legislation of the State of residence, Belgium. In response, the Netherlands Government argued that the work performed in Belgium was too negligible to be considered, thereby making him subject to Dutch legislation for the entire period, under lex loci laboris.

Advocate General Szpunar, in his Opinion to the Court, reiterated that the referring court had outlined three possible outcomes in its request: (a) disregard the activities pursued in Belgium and apply the main rule pointing to the applicable legislation of the State of employment; (b) consider these activities under lex loci laboris, resulting in the applicable legislation changing every time the location of the actual work performed switched between the Netherlands and Belgium; or (c) apply the multi-activity rule, making X subject only to the legislation of the State of residence. ⁸⁷ He then framed the crux of the matter as whether X's activity in Belgium ‘should be taken into account for the purposes of applying those provisions’. If considered, X would be regarded as normally employed in the territory of two Member States under the multi-activity rule. Otherwise, lex loci laboris would apply. ⁸⁸

The Court followed its Advocate General and reframed the questions referred to it, essentially inquiring whether X should be considered to be normally employed in the territory of two Member States within the meaning of the multi-activity rule. ⁸⁹ Having emphasised the subsidiary nature of lex loci domicilii and the risk of circumvention, the Court concluded that the multi-activity rule did not apply in circumstances such as those in the main proceedings. ⁹⁰ While the Court did not elaborate on the specific consequences with respect to lex loci laboris, it is reasonable to infer – based on the question referred and the arguments put forward by both parties and the Advocate General – that if the work performed in Belgium was deemed too insignificant to qualify as multi-activity, it should be disregarded entirely in determining the legislation applicable (see also Jorens, 2022: 329; Van der Mei and Van Ooij, 2022: 135–136). In the main proceedings, the referring court thus ruled that X was subject to Dutch legislation, including for the periods he worked from Belgium. ⁹¹

Conclusions

Article 11(3)(a) of Regulation (EC) 883/2004 should not be construed as automatically altering the applicable legislation under lex loci laboris in cases of cross-border remote work. A change in applicable legislation is triggered when a cross-border activity exceeds a threshold of significance. Only then must workers, employers and national authorities take measures to prevent the change, such as invoking exceptions for posting or multi-activity or negotiating bilateral agreements.

More specifically, marginal activities under Article 14(5b) of Regulation (EC) 987/2009 should be disregarded when assessing simultaneous and alternating working patterns under lex loci laboris. This allows the ‘usual’ State of employment to retain jurisdiction, thereby ensuring continuous affiliation for workers. The wording of Article 11(3)(a) of Regulation (EC) 883/2004 does not contradict this interpretation, which is supported by its context and purpose. ⁹²

It is important to emphasise that marginal activities remain relevant for calculating benefits and contributions under the legislation of the competent Member State (Administrative Commission, 2013: 27; Jorens, 2022: 329). Moreover, this interpretation should not be misconstrued as a blanket exemption for marginal activities under all conflict rules. It is settled case law that lex loci laboris applies to minor part-time or casual work under on-call contracts, thereby making workers with marginal employment subject to the legislation of their State of employment instead of their State of residence. ⁹³

The principal takeaway is that the presumption of territorial immediacy under lex loci laboris – and the associated risk of a ping-pong effect – is more nuanced than often assumed. The determination of the legislation which applies to an employee engaged in cross-border remote work for the same employer can be summarised in three steps:

Determine whether the remote work performed in the host State constitutes a marginal activity under Article 14(5b) of Regulation (EC) 987/2009. Activities accounting for less than approximately 5% of the worker's total working time and/or remuneration should be disregarded under Article 11(3)(a) of Regulation (EC) 883/2004;

If the remote work is not marginal, assess whether it qualifies as posting or multi-activity. Occasional and temporary cross-border remote work falls within the scope of Article 12 of Regulation (EC) 883/2004, whereas remote work as part of a fixed and regular routine is governed by Article 13. If the posting rule applies and the conditions for posting are not met, temporary cross-border remote work will result in a change in applicable legislation under lex loci laboris; and

If the multi-activity rule applies, ascertain whether the worker is subject to the legislation of the State of residence or the State of establishment. Under Article 13(1)(a) of Regulation (EC) 883/2004, lex loci domicilii applies if more than 25% of the working time and/or remuneration stems from activity at home. If, however, the remote work is carried out using information technology connecting the employee to the employer's working environment, the employee may request to remain subject to the legislation of the employer's State of establishment, provided that telework in the State of residence accounts for less than 50% of the total working time and both Member States are signatories to the Framework Agreement on habitual cross-border telework.

One remaining issue concerns the treatment of multiple marginal activities within such an assessment. The answer is clear when employees work for the same employer across two Member States. In the X judgment, the ECJ adopted a holistic approach, concluding that remote work carried out within an alternating working pattern from the State of residence, accounting for 6.5% of the working time, was insufficient to qualify as multi-activity. ⁹⁴ The law is less clear, however, when employees work for different employers or across multiple Member States. The Administrative Commission (2013: 27) has held that marginal activities must be assessed separately for each Member State and cannot be aggregated. As Jorens (2022: 330–331) rightly observes, such an interpretation may put workers with several minor engagements in different Member States at a disadvantage, as they may fail to meet the criteria for multi-activity. While disregarding marginal activities under lex loci laboris may partially mitigate the risk of a ping-pong effect, such an approach still relies on the usual State of employment as a ‘base’ to which the worker regularly returns. For highly mobile workers who may not return to the Member State where their work was previously considered non-marginal, it may be more appropriate to aggregate successive marginal activities when applying the multi-activity rule, thereby making such workers subject to the legislation of their State of residence. ⁹⁵