New EU ruling reshapes A1 certificate calculations: third country work must be included
A recent judgment from the European Court of Justice (C-743/23, A vs. GKV-Spitzenverband) has introduced a decisive change to how cross-border employment is assessed under EU social security rules. Delivered on 11 December 2025, the ruling clarifies that when determining whether an employee performs a “substantial part” of their work in one country, all work must be considered including that performed outside the EU, EEA or Switzerland.
This shift has significant implications for Danish companies, particularly those operating in industries where international mobility is part of everyday operations. From shipping and oil and gas to tech and finance, employers must now revisit how they approach A1 certificate assessments and the choice of applicable legislation.
C-743/23, A vs. GKV-Spitzenverband
The case involved a German resident individual employed by a Swiss company. Over a period of five years, his work pattern included some time in Switzerland, some working remotely from Germany, and the remainder in countries outside the EU framework.
His work pattern concluded:
- 10.5 days per quarter in Switzerland
- 10.5 days per quarter working from home in Germany
- The rest of the time in third countries (countries outside EU/EEA/Switzerland)
The German authorities evaluated only his work within the EU and Switzerland, and concluded that German legislation applied.
But this did not reflect the true picture as the individual worked outside the EU for the majority of the time. Once the court included all work including in third countries, it became clear that only a small proportion of his time was spent in Germany or Switzerland.
The conclusion: Switzerland, as the employer country, was the correct basis for social security affiliation.
The Court’s decision rests on Article 13(1) of Regulation 883/2004 (which covers multi-state employment) and Article 14(8) of Regulation 987/2009. The Court stated that when calculating whether an employee performs a “substantial part of activities” in one country — the 25% threshold — you need an overall assessment of all work. That means total working time globally, not just time spent within the EU/EEA framework.
In this case, when only EU/Switzerland work was counted, Germany looked like the main location as more than 25% of the EU/EEA and Swiss work were carried out in Germany. But when all work was included, Germany accounted for just 16% of total working time.
What does this mean for Denmark?
While the case concerned a Swiss company, the precedent applies across the EU/EEA. Denmark, as a country deeply involved in cross-border employment, is directly affected. Danish nationals working for foreign employers, international staff based partly in Denmark, and mobile teams spanning several jurisdictions — all may now find their social security positions altered by this ruling.
The key takeaway is simple: when evaluating whether someone works “substantially” in a country (generally understood as 25% or more), you can no longer exclude third country work from the equation. Doing so risks misapplying the rules and issuing incorrect A1 certificates.
Three typical situations
This ruling, together with earlier ECJ decisions, gives us a clearer framework for handling international work. Here are three real-world situations now easier to assess:
1. Working across borders, including third countries (following the logic of Case C-743/23)
Take a Danish national employed by a Norwegian shipping company. She spends some time in Denmark and Norway, but the majority of her work takes place on vessels in international waters. Previously, employers might have ignored this offshore time, leading to the assumption that Denmark was the primary place of work. Now, the reality of her work distribution must be recognised and it may mean Norwegian legislation applies instead.
2. Third country work, but regular touchpoints with the employer country (consistent with ECJ Case C-471/18)
Now imagine an Irish engineer employed by a Danish oil and gas firm. He is offshore most of the time, but travels to Denmark several times a year for project meetings and safety briefings. That limited contact is significant. Even though most work is done abroad, the fact that he returns regularly to Denmark means Danish legislation may apply.
3. Entirely remote, with no physical presence in the employer country (as established in ECJ Case C-631/17)
Consider a French software developer working remotely from Southeast Asia for a Danish company. She does not travel to Denmark, does not participate in in-person training or meetings, and works entirely remotely. In that case, it is the residence country (France) that determines the social security position.
An important clarification: While third country work must be counted when determining which country’s social security legislation applies, the A1 certificate itself only grants exemption within the EU/EEA, Switzerland, and (in some cases) the UK. It does not create rights or exemptions for work performed in third countries themselves. Separate considerations may apply for social security obligations in those jurisdictions, including verification with bilateral agreements with said third country.
What Danish companies should do now
This ruling means companies must take a closer look at how they gather and assess information about their mobile employees.
Revisit A1 certificates
If you have applied for A1s based on outdated assumptions, reassess them using the full scope of global activity. Even certificates already issued may be incorrect if they ignored substantial third country work.
This is a reinterpretation of existing rules rather than an entirely new regulation, which means authorities may apply it retroactively. We recommend reviewing A1 certificates issued in the past 2-3 years, particularly if they involve employees with significant third country work exposure.
Improve data collection
Make sure data collection processes for new assignments include questions about global work distribution, not just EU/EEA presence. Capture details about training, meetings or time spent in Denmark, even if only a few days per year.
Authorities will require clear documentation of third country work going forward. For seafarers, this typically means voyage records and logbooks. For other mobile employees, time tracking systems and detailed travel records become more important than ever.
How Crossbord can support
At Crossbord, we handle hundreds of A1 applications annually for Danish and Nordic businesses. That means we have seen most scenarios — and we know which details authorities focus on and what documentation they require.
We have already adjusted our analysis processes following this ruling. For new applications, we now systematically map global work distribution from the outset, including third country activity.
Our approach integrates A1 coordination with broader cross-border compliance. For most clients, the A1 is not a standalone task. Instad, it is part of managing Danish payroll, tax reporting, and ongoing employment compliance as support from The Crossbord Solution.
When the A1 analysis says Danish legislation applies, that conclusion flows directly into payroll execution. When it says another country applies, we coordinate with that country’s requirements and ensure Danish reporting obligations are still met where relevant.
What this means practically: when an employee’s work pattern changes — they move from 30% Denmark to 20% Denmark because of increased remote work time, for example, we register it as part of monthly payroll processing and adjusts accordingly. The A1 position gets reassessed, authorities are notified if needed, and payroll adjusts accordingly. It’s not treated as a separate compliance exercise that happens once and gets forgotten.
If you are uncertain how this ruling affects your organisation — particularly if you have applications currently in the pipeline with Danish authorities or employees with significant third country exposure — we are ready to assist.
Get in touch now to review your existing A1 arrangements and ensure they reflect the new legal reality.
