International employment contract: secondment vs expatriation

Sending an employee to work abroad seems simple on the surface. In reality, the choice between secondment and expatriation has profound consequences for the employment contract, social contributions, personal taxation and employer liability. Confusion between these two regimes can expose the company to URSSAF adjustments, double taxation and costly employment tribunal disputes. In 2026, with strengthened cross-border controls within the European Union and the generalisation of the Posted Workers Directive (2018/957/UE), mastering these distinctions has become an absolute priority for HR and legal departments. This article compares the two statuses point by point, their social security regime, tax treatment and essential contractual safeguards.

Secondment and expatriation: definitions and legal foundations

Before analysing the differences, it is necessary to establish precise definitions, as the boundary between the two regimes is regularly misunderstood in companies.

Secondment: a link maintained with the home system

International secondment is the situation in which an employer temporarily sends an employee to exercise their activity in another country, whilst maintaining their original employment contract with the home company. The seconded employee retains their affiliation to the social security scheme of their sending country, subject to complying with the conditions laid down by European regulations or applicable bilateral conventions.

In European law, Regulation (EC) No. 883/2004 on the coordination of social security systems provides that a seconded employee remains affiliated to the scheme of the sending Member State for a maximum period of 24 months, provided that:

• the foreseeable duration of secondment does not exceed 24 months;
• the employee is not sent to replace another seconded person;
• the employer carries out substantial activity in the sending State (the so-called "substantial activity" criterion).

This affiliation is evidenced by form A1 (or E101 for certain third countries), issued by the social security body of the home country. This document is essential: without it, the employee may be required to pay contributions in the host country, creating a double contribution.

On employment law matters, Directive 96/71/EC as amended by Directive 2018/957/UE imposes on the seconded employee a core of mandatory rights of the host country: minimum wage, maximum working hours, statutory paid leave, health and safety rules. Since 30 July 2020, if secondment exceeds 12 months (extendable to 18 months on justification), all employment conditions of the host country become applicable, except for rules on the establishment and portability of supplementary pensions.

Expatriation: a break with the home system

Expatriation is based on an inverse logic. The expatriate employee is hired locally or offered an expatriation contract that suspends or terminates their original employment contract. They leave the French social security scheme and join that of the host country. In France, the employer may nevertheless opt, with the employee's agreement, to maintain voluntary coverage under the general scheme via the Caisse des Français de l'Étranger (CFE), subject to specific contributions.

Unlike secondment, no maximum duration is imposed on expatriation. The situation is designed to last indefinitely, often several years. The expatriate employee is subject to the host country's labour legislation in full, which implies a thorough analysis of employment law in the host country, particularly regarding dismissal, end-of-contract indemnities and union representation.

Social security regime: practical differences

Secondment: portability of social rights

The main advantage of secondment lies in the portability of social rights: the employee continues to accumulate retirement rights in their home scheme, benefits from health insurance coverage under their usual system (via the European Health Insurance Card in the EU) and pays contributions to supplementary schemes ARRCO/AGIRC if they are French.

For non-EU countries, France has concluded more than 40 bilateral social security conventions (with the United States, Canada, Japan, Brazil, etc.) which organise similar mechanisms. In the absence of a convention, the risk of double contribution is real: the employee and employer can be subject to tax in both States simultaneously.

Expatriation: local affiliation and protection to be rebuilt

In expatriation, the employee joins the local scheme, which means that their future rights depend on the generosity and stability of the foreign system. For destinations with weak social protection, subscription to the CFE and supplementary private insurance (medical cover, income protection) becomes essential. This additional cost can represent 10 to 20% of the total cost of mobility depending on the countries.

The administrative management of expatriation is also heavier: the employer must ensure compliance with registration obligations with local social authorities, subject to sometimes significant penalties. For HR teams managing several simultaneous mobilities, tools dedicated to managing international employment contracts allow centralising documents and securing each step of the process.

Taxation: tax residence, conventions and income taxation

The determining criterion of tax residence

In tax matters, the central concept is that of tax residence. Under French law, Article 4 B of the General Tax Code (CGI) considers as French tax residents persons who have their home or main place of residence in France, whose main professional activity is carried out in France, or who have the centre of their economic interests in France.

An employee seconded for fewer than 183 days per year in a foreign country generally retains their tax residence in France and remains liable to taxation there on all world income (subject to bilateral tax conventions). Conversely, an expatriate who genuinely transfers their home to the host country may lose their French tax residence, which has major consequences: they are liable to taxation in France only on income from French sources.

Bilateral tax conventions: anti-double taxation tool

France has signed more than 130 tax conventions designed to avoid double taxation. These conventions generally follow the OECD model and assign the right to tax salaries to the State where the activity is carried out, unless the employee is tax resident in the other State, does not stay there for more than 183 days and is paid by a non-resident employer.

For short secondments (less than 183 days), the convention often maintains taxation in France. For long-term expatriates, it transfers taxation to the host country. But some conventions contain specific provisions for pension schemes, stock options or passive income that complicate the analysis.

Practical implication for the employer: the mission letter and the remuneration package

In practice, the employer must carefully structure the international remuneration package: maintenance of basic salary, expatriation allowance (often 10 to 15% of gross salary), housing provision, children's schooling, annual return ticket. Each element has different tax treatment depending on whether it constitutes reimbursement of professional expenses or taxable benefit in kind.

The management of these complex contractual documents — amendments to the contract, mission letters, mobility policies — benefits from being digitised and secured. For HR teams managing several mobilities, Certyneo's electronic signature solution for HR enables these documents to be signed remotely, with evidential value equivalent to a handwritten signature.

Contractual obligations and administrative formalities

The secondment contract: content and safeguards

The secondment contract or amendment must mandatorily mention, in accordance with Directive 2019/1152/UE on transparent and predictable working conditions:

• the foreseeable duration of secondment;
• the currency of salary payment;
• cash or in-kind benefits related to secondment;
• repatriation conditions;
• applicable law (generally the law of the original contract, supplemented by the mandatory core of the host country).

It is strongly recommended to add a repatriation clause specifying the modalities of return in the event of illness, accident or early termination of secondment, as well as a choice of law clause under Regulation (EC) No. 593/2008 (Rome I).

The expatriation contract: structure and points of attention

The expatriation contract can take two forms:

1. Amendment to the existing employment contract, which suspends the original contract and specifies the conditions for return to France;
2. Local contract concluded directly with a foreign subsidiary, which then terminates the French contract (risky option as it deprives the employee of acquired rights in France).

The first form is the most protective for the employee and the least risky for the company. It must explicitly provide for: the maintenance or otherwise of acquired benefits (seniority, classification), conditions for reinstatement at the end of expatriation, and the fate of the contract should the foreign subsidiary cease to exist.

In any case, the legal value of electronic signature on these documents is fully recognised in European law, which facilitates the conclusion of cross-border deeds without physical travel.

Unavoidable administrative formalities

Beyond the contract, several formalities are mandatory:

• Form A1 for secondees in EU/EEA/Switzerland: to be requested from URSSAF before departure;
• Prior notification of secondment in the host country (mandatory in all Member States since Directive 2014/67/UE);
• Designation of a representative of the company in the host country (mandatory in many States, including France for foreign companies);
• Registration with local tax authorities if the duration exceeds the thresholds of the applicable convention.

All of these documents benefit from being archived in an electronic and secure manner. The dematerialised pay slip and archiving of contracts with time-stamping constitute evidence that can be relied on in the event of inspection by French or foreign authorities. For more information on the evidential value of time-stamping of documents, Certyneo's guide to electronic time-stamping details the applicable certification levels.

Comparative summary table: secondment vs expatriation

| Criterion | Secondment | Expatriation | |---|---|---| | Duration | Limited (max. 24 months in EU) | Unlimited | | Employment contract | Maintained with original employer | Suspended or replaced by local contract | | Social security | Home scheme maintained (form A1) | Host country scheme | | Tax residence | Generally maintained in France | May be transferred | | Employment law | Mandatory core of host country | Full local law | | Employee protection | High (acquired rights preserved) | Variable depending on host country | | Administrative complexity | Moderate (form A1, prior notification) | High (local registration, CFE, conventions) |

This comparative summary confirms that there is no universally preferable regime: the choice must result from a case-by-case analysis taking into account the foreseeable duration, the host country, the employee's tax profile and the company's strategic objectives. HR teams can rely on Certyneo's AI-powered contract generator to produce draft amendments compliant with the requirements of each regime, to be subsequently validated by specialist advice.

Legal framework applicable to international mobilities

The management of international mobilities falls within a layering of European, international and national standards that must be mastered to avoid any risk of non-compliance.

European Union law

Regulation (EC) No. 883/2004 of the European Parliament and of the Council, as amended by Regulation (EC) No. 987/2009, is the cornerstone of the coordination of social security systems within the EU, the EEA and Switzerland. It establishes the principle of the unity of applicable legislation and organises the modalities of secondment (Article 12) and multi-State situations (Article 13).

The Directive 96/71/EC on the posting of workers, fundamentally revised by Directive 2018/957/UE (transposed into French law by Ordinance No. 2019-116 of 20 February 2019), defines the minimum rights applicable to seconded employees in the EU: remuneration, working hours, accommodation conditions and the core of collective agreements.

Directive 2019/1152/UE on transparent and predictable working conditions imposes new standards of contractual information, particularly for mobile workers (Articles 7 to 9).

Regulation (EC) No. 593/2008 known as "Rome I" governs the law applicable to contractual obligations, allowing the parties to choose the law applicable to the international employment contract, subject to not depriving the employee of the mandatory provisions of the objectively applicable law.

International tax law

Bilateral tax conventions predominantly follow the OECD Model (2017 version, updated in 2024). Article 15 of the OECD Model governs the taxation of employment income. In France, Article 4 B of the General Tax Code determines tax residence, and Article 81 A of the CGI provides for an exemption from income tax for certain employees seconded abroad under strict conditions (period of presence abroad exceeding 120 or 183 days depending on the activity).

French employment law

Articles L. 1261-1 to L. 1266-1 of the Labour Code transpose the Posted Workers Directive into French law. They provide in particular for the obligation to notify in advance employers posting employees in France and the criminal and administrative penalties applicable in case of failure (fine of up to € 500,000).

Security of acts and digital documentation

Electronic signature of international mobility contracts is governed by Regulation eIDAS No. 910/2014 (currently being revised under eIDAS 2.0) which confers full legal value on advanced and qualified electronic signatures. The GDPR No. 2016/679 applies to the processing of personal data of employees in the context of mobility procedures, in particular for the transfer of data outside the EU to third countries (Articles 44 to 49).

Use scenarios: international mobilities in practice

Scenario 1 — A mid-sized industrial company managing frequent intra-European secondments

A mid-sized industrial company with approximately 1,200 employees and subsidiaries in five EU Member States carries out between 40 and 60 secondments of short and medium duration (3 to 18 months) each year for assembly, maintenance and technical training missions. Before digitising its processes, its HR teams managed all Form A1s, secondment amendments and prior notifications on paper support, with average processing times of 12 working days per file.

By deploying an integrated management and electronic signature solution, the company reduced this timeframe to an average of 2.5 days, whilst reducing data entry errors by 65%. Time-stamped archiving of signed Form A1s and amendments enabled the company to respond in less than 48 hours to two consecutive labour inspections in different host countries, without penalty. ROI was reached in less than 8 months according to the finance department's internal estimate.

Scenario 2 — A professional services group managing long-term expatriations outside the EU

A consulting and engineering group of approximately 3,500 employees sends around fifteen senior managers each year on long-term expatriations (3 to 5 years) to countries in South-East Asia and sub-Saharan Africa, areas poorly covered by bilateral social security conventions. The complexity of each file — expatriation contract, amendment suspending the French contract, CFE membership, mission letter, international remuneration policy — represented on average 22 hours of administrative work per file.

The implementation of a digital platform centralising the production, signature and archiving of documents made it possible to reduce the administrative burden by 40% and eliminate incidents related to unsigned or lost contract versions. The ability for employees to sign their documents from their future place of assignment, without physical return to France, was identified as a factor improving the candidate experience in terms of mobility.

Scenario 3 — A hyper-growth tech start-up recruiting its first employees abroad

A French SaaS start-up, recently raised in Series B, hires for the first time three employees in the United Kingdom and Germany, whilst considering temporary secondment of two French engineers to Berlin for an 8-month ramp-up phase. The HR team, consisting of a single person, has no prior experience with international mobilities.

By relying on a contract generator adapted to secondment and expatriation regimes, supplemented by an electronic signature solution compliant with eIDAS, the start-up was able to produce and have secondment amendments signed that comply with Directive 2018/957/UE in less than 72 hours per file. Form A1s were obtained from URSSAF before the two engineers' departure, avoiding any risk of double affiliation. The management estimated approximately €8,000 in legal fees avoided thanks to the automation of the first levels of documentary compliance, whilst retaining validation by specialist advice for complex tax aspects.

Conclusion

Secondment and expatriation are two fundamentally distinct regimes, with profound consequences for the employee's and employer's employment contract, social security and taxation. Secondment offers portability of social rights and valuable contractual continuity, but imposes a limited duration and compliance with the mandatory core of the host country. Expatriation offers greater flexibility in duration, but requires a complete reconstruction of social protection and in-depth tax analysis.

In both cases, the quality of contractual documentation — amendments, mission letters, Form A1s, prior notifications — is decisive for compliance and legal security of the mobility. Certyneo enables you to produce, have signed and archive these documents remotely, with full legal value, regardless of the employee's location.

Discover how Certyneo secures your international mobilities or estimate your return on investment today.