Your employee is heading to London, Barcelona, Milan or Singapore. A few weeks, a few months, perhaps longer. On the surface, it seems straightforward: they carry on working for you, just from another country. And yet, behind this international mobility lies a reality that many companies discover far too late — at great cost.

Posting a Swiss employee abroad touches simultaneously on employment law, social insurance, taxation and the local regulations of the host country. Which means the pitfalls are many, and a single mistake can prove very expensive indeed.

What exactly is a posted worker?

We speak of a posting when a company temporarily sends one of its employees to work in another country, whilst maintaining the employment relationship with the original employer. The employee remains employed by their Swiss employer and affiliated to the Swiss social insurance system, but carries out their work on foreign soil.

This is quite different from a permanent transfer or long-term expatriation. And yet, even for a mission of just a few weeks, the legal obligations stack up quickly.

Five dimensions to manage simultaneously

1. Social security: where are contributions paid?

This is usually the first question — and the thorniest. In Switzerland, social insurance (AVS/AHV, AI/IV, APG/EO, AC/ALV, LPP/BVG, LAA/UVG) covers employees residing and working on Swiss territory. The moment your employee leaves the country to work abroad, the default rule changes.

The answer depends first and foremost on the destination:

Destination	Applicable framework
EU / EFTA	Règlement (CE) nRegulation (EC) No 883/2004 — country-of-employment principle
Countries with bilateral agreement (e.g. USA, Canada, Australia)	Specific convention to be analysed case by case
Countries without convention	Risque de double cotisaRisk of double contributions or gaps in coverage

Where a social security agreement exists between Switzerland and the host country, it is generally possible to obtain an A1 certificate (for EU/EFTA) or an equivalent document. This certificate confirms that the employee remains affiliated to the Swiss system for the duration of the posting.

Without this document, your employee could find themselves required to contribute in both countries simultaneously — or, worse, not be properly covered in either.

Worth noting: the maximum posting duration covered by agreements varies. It is generally 24 months for EU/EFTA countries, but may differ under bilateral agreements. Beyond this period, an extension request is possible in certain cases, though by no means guaranteed.

2. Local employment law: which rules apply in the host country?

A posted Swiss employee remains subject to their Swiss employment contract. But this does not exempt them — or you — from the mandatory rules of the country where they are working.

In Europe, Directive 96/71/EC on the posting of workers (and its 2018 revision) requires employers to comply with certain minimum conditions of the host country, including:

• Maximum working hours and rest periods
• The statutory or collective minimum wage
• Health and safety at work regulations
• Statutory annual leave entitlement

This principle applies from day one. Ignoring local regulations — even for a two-week assignment — can expose the company to administrative penalties in the host country.

Practical example: a Swiss consultant sent to France must receive remuneration at least equivalent to the French SMIC (or the applicable collective wage if higher). If their Swiss salary is already higher, there is no issue. If not, a reclassification may follow.

3. Taxation: who taxes what?

Tax is often the dimension that surprises HR managers and finance directors the most. An employee who physically works in a foreign country may create a tax obligation there — for themselves, but sometimes for the company as well.

Two major risks:

For the employee: depending on the length of physical presence in the host country and the applicable tax treaties, the employee may become taxable — partially or fully — in that country. Thresholds vary: 183 days as a general rule (the so-called 183-day rule in OECD model conventions), though some countries apply lower thresholds or different criteria altogether.

For the company: if the employee carries out commercial or representative functions in the host country, this may constitute a permanent establishment in the eyes of the local tax authorities. The consequence? The company could become liable for corporation tax in that country — even without having opened a branch or subsidiary there.

This permanent establishment risk is one of the least well-known and most costly. It is particularly relevant for commercial or business development missions.

4. Administrative formalities in the host country

Depending on the destination, your employee may need to:

• Obtain a work visa or specific permit (outside the EU/EFTA area, Schengen freedom of movement does not confer the right to work legally)
• Register with local authorities (some countries require registration from the very first days of presence)
• Comply with prior notification procedures: in France, Belgium, Germany or Austria, the Swiss employer must declare the posting before the assignment begins, sometimes with a mandatory lead time

These formalities may seem minor. They are not. In France, for instance, failure to submit a prior posting declaration exposes the company to a fine of up to €4,000 per employee concerned.

5. Supplementary social protection: beware of coverage gaps

During the posting, does your employee have accident cover abroad? Does their income protection insurance cover incapacity occurring outside Switzerland? Is their occupational pension scheme (LPP/BVG) maintained on the same terms?

These questions may sound technical. But in the event of an accident or illness abroad, coverage gaps can have devastating consequences for the employee — and serious legal and financial repercussions for the company.

A compounding complexity that leaves no margin for error

Vous l’aurez compris : le détachement international ne se pilote pas d’un seul tableau de bord. Il nécessite de coordonner siAs you will have gathered: an international posting cannot be managed from a single dashboard. It requires the simultaneous coordination of:

• Swiss social security rules and those of the host country
• Local employment law
• Taxation in both countries
• Country-specific administrative formalities
• Complete insurance coverage

And all of this, often, within tight timeframes, with counterparts in multiple countries and languages.

The slightest error or omission can generate penalties, tax reassessments or disputes — sometimes years after the mission has ended.

What changes when you have the right support

Bien structuré, un détachement international est une opportunité réelle pour les entreprises qui cherchent à déployer leurs tProperly structured, an international posting is a genuine opportunity for companies looking to deploy their talent wherever the mission demands. It simply requires anticipating every dimension from the outset:

• Checking whether a social security agreement applies and obtaining the necessary certificates
• Analysing the tax obligations for both the employee and the company
• Identifying the declaration requirements in the host country
• Adapting the employment contract where necessary
• Ensuring that social coverage remains complete throughout the duration of the assignment

At Opsys360, we support companies and professionals through these complex situations. Our expertise in payrolling and HR support allows us to secure every stage of the posting — from administrative preparation to the close of the mission — so that you never have to become an expert in international employment law yourself.

Because an international assignment should be an opportunity, not a risk.

Our experience has taught us that things run better when everyone involved can engage with confidence. If you would like support to ensure everything is clear, compliant and straightforward, do not hesitate to contact our HR experts.