Cross-border worker: tax and social contributions (Switzerland, Luxembourg, Belgium)

Quick answer. A cross-border worker lives in one country and works in the neighbouring country. Their taxation and contributions depend on the country of employment and the applicable agreements. The most frequent trap in 2026 is to confuse two distinct remote-work thresholds: the tax threshold (for France and Switzerland, 40% of remote work tolerated, in force since 1 January 2026) and the social threshold (up to 49.9% of remote work in the country of residence without changing the social affiliation, under the European framework agreement). On the tax side, Switzerland has a particular regime by canton; Luxembourg and Belgium tax in principle at the place of work.

Hundreds of thousands of employees living in France work in Switzerland, Luxembourg or Belgium. The rise of remote work has upended their situation: where are they taxed? To which social scheme do they contribute? And above all, how many days can they work remotely from France without tipping everything over? The answers differ by country and, crucially, depending on whether you reason in tax or social terms. The subject extends our analysis of remote work abroad.

The cross-border worker lives in one country and carries on their salaried activity in the neighbouring country, where they go regularly. Their tax and social regime cannot be deduced from a single principle: it results from the applicable tax treaty, specific cross-border agreements and the European social-security rules. Two questions must therefore be handled separately: where the salary is taxed, and to which social scheme the employee contributes.

• Switzerland. The regime is particular and varies by canton. For eight cantons covered by the 1983 agreement (Bern, Solothurn, Basel-City, Basel-Country, Vaud, Valais, Neuchâtel, Jura), the cross-border worker's salary is taxed in France, the country of residence, Switzerland receiving a financial compensation. For the other cantons, notably Geneva, the salary is taxed at source in Switzerland.
• Luxembourg. The salary is in principle taxed in Luxembourg, the place of work, under the tax treaty.
• Belgium. The salary is in principle taxed in Belgium, the place of work, the former cross-border regime having ended.

This is the trickiest point. Remote work from France follows two distinct logics, with different thresholds.

• The tax threshold (Switzerland): 40%. An amendment to the France-Switzerland tax treaty, in force since 1 January 2026, allows up to 40% of remote work per year without challenging the planned taxation (the salary remains taxed as without remote work), a portion of temporary assignments being included in this cap. Beyond 40%, taxation in France may apply to the remote days.
• The social threshold: 49.9%. Under the European framework agreement based on Regulation (EC) no. 883/2004, a cross-border worker can work remotely up to 49.9% of their time in their country of residence without changing their social affiliation: they remain affiliated to the employer's country scheme, subject to an A1 certificate request. Beyond 49.9%, affiliation shifts to the French social scheme.

Confusing 40% (tax) and 49.9% (social) is the most frequent mistake. The same employee may meet the social threshold but exceed the tax threshold, with consequences for their taxation.

In principle, social contributions are due in the country of employment (place of work), in line with the European regulation. Remote work up to 49.9% does not change this affiliation. France-Switzerland cross-border workers also have an option for their health cover (Swiss insurance or French scheme), to be exercised within the deadlines.

The France-Switzerland cross-border worker who works remotely. They must track two counters: not exceeding 40% for tax, nor 49.9% for social. Documented tracking of days is essential.

The Luxembourg cross-border worker. A remote-work tolerance threshold also applies on the tax side (of the order of a few dozen days a year); beyond it, the remote days may be taxed in France. The 49.9% social threshold applies in parallel.

The employee recruited abroad. Bringing in or recruiting an employee in the neighbouring country follows a different logic, distinct from the cross-border status, such as recruiting a foreign employee or organising mobility.

• Two thresholds, two logics. 40% for France-Switzerland tax, 49.9% for social: do not confuse them.
• Document the remote-work days. Precise tracking conditions compliance with the thresholds and the security of the situation.
• The canton matters (Switzerland). Depending on the canton, the salary is taxed in France or at source in Switzerland.
• The health option has a deadline. France-Switzerland cross-border workers must choose their health cover in time.
• The employer has a role. A1 request, remote-work tracking, payroll setup: compliance is shared.

Recently, a cross-border worker working in Switzerland and working remotely two days a week from France asked us, convinced he was "within the rules" because he stayed under 50%. The analysis showed he did meet the 49.9% social threshold, but exceeded the 40% France-Switzerland tax threshold, with taxation in France of the remote days beyond it. We clarified the two counters, adjusted his remote-work organisation and secured his tax and social situation, alongside his employer.

Our conviction, as accountants registered with the Ordre, is that the cross-border workers' situation has become a technical subject in its own right, where intuition misleads. The reflex "less than half, so all is well" is wrong: the social threshold and the tax threshold do not coincide. The good practice is rigorous day-tracking, a precise reading of the applicable treaty and agreement, and coordination with the employer, alongside social management and payroll.

Hayot Expertise advice. If you are a cross-border worker or employ cross-border workers, keep two distinct remote-work counters: 40% for the France-Switzerland tax threshold, 49.9% for the European social threshold. Identify the canton of work (in Switzerland) that determines where the salary is taxed. Document the remote days precisely, exercise the health option in time, and coordinate with the employer on the A1 request and payroll. The "under 50%" rule is a false sense of security: it is the two thresholds, tax and social, that must be met.