International secondments or postings: social security and tax considerations (update 2026)

Secondments and postings abroad are becoming increasingly common. This applies not only to senior management and sales roles, but also to managers, specialists, and project staff. This is often because companies operate internationally, for example in the Netherlands and Germany, or because employees live and work in different countries. What many employers and employees fail to recognise is that working across borders has direct implications for social security and taxation. These two aspects do not always align.   

One employee, one social security system 

The basic principle within Europe is that a person can only be covered by social security in one country. European legislation (EU regulations) determines which country this is. Typically, this is the country in which they work, but exceptions apply in cases of international secondment. If an employee is temporarily seconded to another EU country, they may remain covered by social security in their home country, subject to certain conditions. This prevents double contributions and ensures continuity in areas such as pensions, sickness and unemployment benefits. 

The A1‑certificate: essential proof for international secondments or postings  

The A1 certificate is central to cross-border work. This document shows which country the employee is covered by for social security purposes. Without an A1 certificate, you, as an employer, risk: 

• double social security contributions
• fines following inspections abroad
• lengthy discussions with the authorities
• dissatisfied employees.

Experience shows that inspections abroad are becoming increasingly common. Thorough advice and an A1 certificate are therefore not mere formalities, but a necessary foundation. 

Social security and taxation do not automatically coincide  

It is a common misconception that social security and taxation automatically coincide. This is not the case.  
It is not uncommon for: 

• social security contributions to remain payable in the Netherlands, 
• whilst income tax must be paid (in part) in the country of employment, for example Germany. 

A comprehensive assessment is essential, particularly in the case of intra-group secondments or when work is carried out in multiple countries. 

International secondments The Netherlands – Germany: very common, often complex 

In practice, we often see cross-border work between the Netherlands and Germany being assessed incorrectly. This applies to Dutch employees temporarily working in Germany (or vice versa), as well as to directors and major shareholders with activities in both countries. Misunderstandings regarding social security obligations, payroll taxes and employer status for tax purposes can quickly arise in these situations. The Tax Treaty between the Netherlands and Germany is therefore important for determining the right to tax wages or other remuneration. 

Practical tips for international secondments or postings 

• Start assessing social security and tax obligations well in advance. 
• Arrange for the A1 certificate before work commences. 
• Always set out agreements regarding duration, duties and authority in writing. 
• Have social security and tax matters assessed separately and together. 

NeD Tax advises business owners and employees on international secondments and assignments. We provide clarity, minimise risks and prevent unpleasant surprises later on. 

Would you like to know where you stand? Please feel free to contact us.