A mid-market company with 350 employees deploys three engineers to Germany for 18 months, manages two cross-border workers who live in Belgium and commute to its Lille office, and has just hired a sales director based in Singapore on a local contract. Three situations, three distinct regulatory regimes, three different payroll treatments. Most generalist ERPs do not make this distinction natively. HR departments bear the consequences: social security audits, missing A1 certificates, undeclared local social coverage.
International employee mobility is growing rapidly across Europe. According to the European Commission’s annual report on intra-EU labour mobility, 2025 edition, 10.1 million European citizens work in another Member State in 2024, including 1.83 million cross-border workers. These are real employees, real payslips, real compliance obligations. Is your HRIS ready to handle this complexity?
Why International Mobility Exposes Mid-Market Companies to Underestimated Risks
The 3 Types of Mobility: Posting, Expatriation, Cross-Border Work
Confusing these three statuses is the most common starting mistake. It leads to applying the wrong legal and social regime — often without anyone realising until an audit.
Posting covers an employee who remains employed by their home company, continues to contribute to their home country’s social security, and temporarily works in another state. The standard maximum duration for maintaining home-country social security coverage is 24 months. However, EU Directive 2018/957 requires that posted workers receive the working conditions of the host country from day one (minimum wage, working time), and that after 12 months of presence, virtually all local employment law applies.
Expatriation applies to an employee who relocates permanently to another country, generally for more than 24 months or under a local contract in the host country. The employee progressively exits their home country’s social security regime. The employer must arrange social protection in the host country (or via private insurance such as the CFE, AXA International or Cigna) and manage payroll in the local currency.
Cross-border workers live in one country and regularly work in a neighbouring country, typically returning home at least once a week. Their tax and social situation is governed by specific bilateral conventions: France–Switzerland, France–Belgium, France–Luxembourg — each with its own rules on tax residency and the competent social security fund.
The Concrete Risks: Audits, Permanent Establishment, Social Penalties
A posted employee without an A1 certificate exposes the employer to double contribution: the employee may be subject to the host country’s social security in addition to the home country’s, creating an unbudgeted cost overrun. In many European countries, social security authorities audit companies where postings were not properly declared or the A1 certificate was not obtained before departure.
The risk of tax permanent establishment is less well known but equally real. When an employee spends an extended period in a country and represents the company there with authority to sign contracts, local tax authorities may consider that the company has a permanent establishment in that country — making it liable for local corporate tax on the portion of activity conducted through that employee. Courts across Europe have consistently ruled on this, including a July 2026 decision confirming permanent establishment exposure for a company whose posted workers carried out substantial operations in a foreign jurisdiction.
Key Figures on Intra-European Mobility
In France alone, according to DARES data on posted worker employment in 2023, there were 223,300 posted employees in 2022, representing 0.4% of private-sector employment. The average posting duration is 97 days. The most affected sectors are construction (42%) and manufacturing (31%). For mid-market companies sending their own employees abroad — the reverse flow — the situation is symmetrical: same obligations, same risks, on the sending employer’s side.
The Regulatory Framework Your ERP Must Understand
The A1 Certificate: Cornerstone of Intra-European Posting
The A1 certificate is the central document for postings within the EU. It certifies that the employee remains affiliated to their home country’s social security during the posting. Without this document, the employee risks being affiliated to the host country’s social security from day one, triggering double contributions.
In France, the A1 certificate is issued by URSSAF (the French social security collection agency) through its International Mobility Service, as documented by the CLEISS (European and International Social Security Liaison Centre). The application must be submitted before the posting begins, with a recommended lead time of 4 to 6 weeks. Coverage is valid for a maximum of 24 months. Beyond that, affiliation switches to the host country, unless a derogation is negotiated between the competent authorities of both states.
The equivalent processes run through different bodies in other countries: Germany’s DVKA (Deutsche Verbindungsstelle Krankenversicherung – Ausland), the Netherlands’ SVB (Sociale Verzekeringsbank), the UK’s HMRC for pre-Brexit legacy arrangements. Each has its own administrative lead times and procedures.
A properly configured HRIS automatically triggers the A1 certificate request as soon as an international assignment is created for an employee: the application form is pre-populated, and an alert fires 30 days before departure if the certificate has not yet been received.
Bilateral Social Security Conventions Outside the EU
For countries outside the European Union (Singapore, United States, Morocco, Brazil…), EU member states have concluded bilateral social security agreements that define which regime applies to a mobile employee. Some allow maintenance of home-country affiliation for non-EU postings of up to 3 years; others require immediate local affiliation. Without this upstream verification, the employer faces contributions to two systems simultaneously.
EU Posting Directive 2018/957: Minimum Pay and Duration
Applicable since 1 August 2020, Directive 2018/957 strengthened employer obligations when posting workers within the EU. It requires that posted workers receive remuneration at least equivalent to what a local employee would receive for identical work in the host country, including bonuses, supplements and benefits provided for in the sector’s collective agreements.
After 12 months of presence (or 18 months on a reasoned notification to the host country’s labour inspectorate), the full body of host-country employment law applies. The HRIS must alert at 11 months so the employer can choose between repatriating the employee, formally extending the mission, or switching to a local contract.
Withholding Tax and Double Taxation Conventions
For mobile employees, the general principle under double taxation conventions is that the country where work is performed may tax the income. For cross-border workers, derogating rules apply. The amendment to the France–Switzerland double taxation convention, which entered into force on 24 July 2025 and applies from 1 January 2026, establishes permanent rules on teleworking: a cross-border worker can work from their French home up to 34 days per year without modifying their Swiss tax treatment. Equivalent arrangements apply for Luxembourg and Belgium, with different thresholds (24 days for Luxembourg).
While these specific thresholds apply to the France–Swiss/Belgian/Luxembourg corridors, the underlying issue — the impact of cross-border telework on social and tax affiliation — is now being addressed by similar bilateral agreements across the EU, with further developments expected through 2027.
What the HRIS Must Manage for Each Type of Mobility
Posted Workers (Under 24 Months)
For a posted worker, the HRIS must handle the following.
A1 certificate request and tracking: initiating the filing with the competent authority, tracking receipt, alerting if the certificate has not been received 7 days before departure.
Pay compliance: automatic comparison between the employee’s salary and the legal or collective minimum in the host country. For a posted worker in the German construction sector, this means verifying the SOKA-BAU minima (the German construction sector holiday pay fund), which apply from day one.
Mission duration tracking: alerts at 6 months (operational logistics), 12 months (Directive 2018/957 threshold), 18 months (maximum threshold on notification), and 23 months (decision reminder: repatriate or switch to expatriate status).
Posting expense management: accommodation and transport costs covered by the employer for the purposes of the mission are not treated as remuneration under Directive 2018/957, but must be properly documented to avoid reclassification during an audit.
Expatriates (Over 24 Months or Local Contract)
For an expatriate, the HRIS manages a progressive break with the home country regime.
Affiliation switch: end of A1 certificate, opening of local social coverage or — for French nationals — via the CFE (Caisse des Français de l’Étranger, France’s voluntary overseas social security fund, with 2026 contributions calculated on the basis of the PASS = €48,060 annually). Other EU countries have equivalent voluntary schemes for their citizens abroad; international private cover through AXA International, Cigna or Allianz Care is also commonly used.
Local currency payroll: issuing payslips in the host country’s currency, converting and booking in group accounts in euros or the group’s reference currency.
Split payroll: if remuneration is mixed (one part paid in the home country, one part in the host country), the HRIS calculates two coordinated payslips for the same employee.
Tax equalisation: calculating the theoretical tax liability in the home country, comparing it to the actual tax in the host country, and adjusting so the employee is not financially penalised by mobility. This functionality typically requires a specialist provider (EY Human Capital, Deloitte Global Employer Services, KPMG Expat Services).
Cross-Border Workers
Cross-border workers are often overlooked in HRIS configuration because they appear “ordinary”: they come into the office every day, have a standard employment contract. But their social and tax treatment is specific.
A Franco-Belgian cross-border worker is affiliated to French social security (country of employment under EU Regulation 883/2004). A Franco-Swiss cross-border worker is affiliated to Swiss social insurance (LAMal for health, AVS/AI for retirement). The HRIS must manage these distinct affiliations within the same environment.
From 2026, the telework rules applicable to cross-border workers have evolved under the main bilateral conventions. The HRIS must track the number of days worked in each country for each cross-border worker, and trigger an alert when the thresholds that affect social affiliation are approaching.
HRIS Features Dedicated to International Mobility
A serious HRIS on this topic provides at minimum:
- An assignment management module that distinguishes the type of mobility (posting, expatriation, cross-border, short-duration mission) and automatically derives the applicable social and tax rules
- A document vault: A1 certificates, expatriation contracts, mission letters, double taxation agreements, voluntary social insurance attestations, cross-border telework forms — all archived with timestamps and expiry dates
- Country-specific regulatory alerts: legal thresholds change regularly. Vendors who maintain a regulatory database updated quarterly by country help avoid inadvertent breaches
- Connectors with specialist providers: exporting assignment data in the standard formats used by mobility consulting firms to avoid double data entry
Overview of HRIS Platforms That Natively Handle International Mobility
Workday is the undisputed leader for mid-market and large enterprises. Its Global Payroll module covers more than 40 countries with native international mobility management: A1 certificate requests, split payroll, tax equalisation, cross-border threshold tracking.
SAP SuccessFactors Employee Central Global offers solid international assignment coverage with strong integration for large groups already running SAP. The Employee Central Payroll module handles payroll in 49 countries with locally certified calculation engines.
Oracle HCM Cloud provides comparable coverage to Workday, with a Global HR module that handles regime transitions (posting to expatriation) in an automated fashion.
ADP Global Payroll is an alternative for mid-market companies that prefer to outsource local payroll rather than manage it in-house. ADP ensures compliance in 140 countries and connects to the group’s ERP via API for variable payroll elements.
Ceridian Dayforce and UKG Pro are relevant mid-market options for companies with a limited mobility footprint (5 to 10 countries). Their coverage is less exhaustive than ADP or Workday, but their cost-to-value ratio suits organisations with 200 to 1,500 employees.
Country-specific HR solutions — whether French (Cegid, Silae, Lucca), British (Sage Payroll, Access Group, iTrent) or German (Datev, Agenda) — generally do not handle international mobility natively. For a mid-market company with mobile employees, they require country-by-country local partners or integration with a dedicated expatriate management tool.
For a detailed platform comparison, see our Workday vs SAP SuccessFactors vs Oracle HCM Cloud comparison for European mid-market companies.
Case Study: A Mid-Market Company with Belgian and German Subsidiaries
Consider a company with 420 employees, headquartered in Lyon, a commercial subsidiary in Brussels (40 people) and a production unit in Stuttgart (80 people). It manages six mobility profiles simultaneously.
Two engineers posted Lyon to Stuttgart (14 months): the HRIS generates A1 certificates before departure. At 12 months, it triggers an alert: holiday entitlements must now integrate the rules of the German BurlG (Bundesurlaubsgesetz, the Federal Leave Act). At 13 months, it sends a decision reminder: extend the mission (notification to the German labour inspectorate before 12 months — already missed), switch to a local contract, or repatriate.
Two Belgian cross-border workers commuting to Lille: affiliated to French social security (country of employment). The HRIS tracks the number of telework days from their Belgian home address and alerts at 20 days (social affiliation impact threshold under the current France–Belgium bilateral convention).
A regional manager expatriated to Singapore (local contract): France and Singapore have a limited bilateral convention. The employee exits the French mandatory regime. The HRIS triggers the CFE enrolment process, manages a payroll in Singapore dollars with conversion to euros, and exports compensation elements to the tax equalisation provider.
Six profiles, three countries, different rules for each. Without an HRIS configured for this complexity, each situation is managed manually by HR, with error risk proportional to the number of cases.
HR Checklist: 12 Points to Secure International Mobility in Your ERP
- Mobility type classification: does your HRIS explicitly distinguish posting, expatriation and cross-border work in its assignment forms?
- A1 certificate: is there an automated request process with a pre-departure alert?
- Posting duration tracking: alerts configured at 12 months (Directive 2018/957) and 18 months?
- Host country pay compliance: automatic verification of salary paid vs legal/collective minimum in the host country?
- Split payroll: if required, does the HRIS manage two coordinated payslips for the same employee?
- Tax equalisation: is a specialist provider or dedicated module in place for expatriates?
- Expatriate social protection: is voluntary social insurance enrolment tracked in the HRIS with expiry dates?
- Cross-border workers and telework: is the number of days worked from the country of residence tracked per employee?
- Document vault: are A1 certificates, expatriation contracts, attestations and addenda archived with timestamps and expiry alerts?
- Legal updates: does your vendor contract guarantee updates to legal parameters by country within 30 days of official publication?
- Permanent establishment risk: is your legal team notified of every employee present for more than 6 months in a foreign country?
- Audit trail: are all mobility decisions recorded in the HRIS with timestamps and the name of the decision-maker?
To go further, read our guide on 7 international payroll pitfalls in an ERP and our HRIS comparison for European mid-market companies.
