Avoiding Double Taxation – Tax Residency in Cross-Border Employee Assignments

What does “tax residency” mean?

Tax residency is a core concept in international tax matters, typically defined in Article 4 of DTAs. It determines in which country a person is considered fully liable to tax.

A DTA only applies – and thus only provides protection from double taxation or double non-taxation – if a person is resident in at least one of the involved countries.

Why is proper assessment so important?

Accurate determination of tax residency is crucial in international tax law because it affects:

• Taxation rights: Only the country of residence may tax worldwide income.
• Payroll and withholding tax: Without clear residency, double withholding may occur.
• Compliance: Lack of clarity complicates reporting, documentation, and internal processes.

Dual residency – the most common pitfall

In cross-border situations – for example, during temporary international assignments – a person may be considered fully tax resident in both countries. In such cases, the so-called tie-breaker rule in the DTA applies, considering the following criteria:

1. Permanent home
2. Centre of vital interests
3. Habitual abode
4. Nationality
5. Mutual agreement procedure

Note: Many jump straight to the “centre of vital interests” – but the first step is always to examine the permanent home.

Checklist for HR: Determining Tax Residency Safely

For global mobility newcomers and HR teams – how to systematically avoid tax risks:

1. Is there a double taxation agreement (DTA)?
Check whether a DTA exists between the home country and the host country. Only then do international rules on avoiding double taxation apply.
Quick Tip: Use the official DTA list from the German Ministry of Finance (BMF) for clarity.

2. Determine full tax liability
Clarify whether the employee has a residence or habitual abode in the home country, host country, or both. DTAs only apply when full tax liability exists.
Quick Tip: Carefully document registration periods and locations of stay.

3. Determine residency using the DTA’s tie-breaker rule
If dual residency exists, apply the sequence from Article 4 of the DTA:

• Permanent home
• Centre of vital interests
• Habitual abode
• Nationality
• Mutual agreement procedure
  Quick Tip: Always start with the permanent home – many mistakenly jump to vital interests first.

4. Allocate workdays by country (Work-Day Split)
Identify in which country the work was physically performed. This determines correct payroll taxation and withholding tax obligations.
Quick Tip: Request calendars and travel logs early on.

5. Check payroll obligations
Determine whether payroll tax withholding is required in the host country and whether adjustments are needed to the home country payroll (e.g. relief or credit).
Quick Tip: Involve a local payroll provider early to avoid errors, interest, or penalties.

6. Assess social security separately
Note that tax residency doesn’t automatically determine social security responsibility. Clarify if an A1 certificate or posting is possible.
Quick Tip: Request a social security status certificate for protection.

7. Ensure documentation and communication
Store all key information on residency, workday split, and supporting documents (e.g., certificates) centrally and chronologically.
Quick Tip: Use a standardized one-pager template per assignment for internal and external use.

8. Seek external advice early
In complex cases (e.g., multi-state scenarios, long-term postings, or cross-border home office), external advice should be obtained early.
Quick Tip: Initiate consultation 4–6 weeks before the start of the assignment.

How to concretely avoid double taxation

• Pre-assignment briefing
  Employees understand duties and risks from the start.
• Calendar tracking tool
  Automatic workday allocation reduces errors.
• Global mobility policy
  Standardized processes ensure clarity and legal certainty.
• Use mutual agreement procedures
  In case of tax authority disputes: proactive conflict resolution.

Conclusion

Tax residency is not a bookkeeping detail, but the foundation of a legally sound international assignment. Those who master the tie-breaker rules of DTAs, set up admin processes early, and align payroll and social security avoid risks for both employees and the business.