How do you declare tax when one partner works for an EU institution and the other in Luxembourg?

Tax filing depends on whether the couple is married or in a registered partnership (PACS), and on the tax residency status of the EU institution employee.

For married couples:

Married couples file a joint tax return by default in Luxembourg. The EU institution employee’s income is exempt from Luxembourg taxation and does not need to be declared as taxable income. A certificate of employment from the EU institution must be provided. The couple can claim joint deductions such as mortgage interest or insurance premiums.

For PACS couples:

PACS couples may only file a joint tax return if both partners are Luxembourg tax residents — this is a legal condition for joint taxation of PACS partners. If filing jointly, the EU institution employee must submit a certificate of employment that explicitly indicates their Luxembourg tax residency. If the EU institution employee is not a Luxembourg tax resident, only the Luxembourg-employed partner declares their salary and claims deductions individually.

How to determine the tax residence of a European civil servant?

1. The partner comes to Luxembourg solely to take up employment with a European institution:

• Tax residence remains in the country of origin, even if the couple lives together in Luxembourg.
• Joint taxation under Article 3bis is not possible, as the conditions are not met.

2. The partner was already living in Luxembourg or came for a reason other than taking up employment:

• In this case, tax residence is considered to be in Luxembourg and joint taxation under Article 3bis is possible, provided that the civil partnership existed throughout the year and the partners shared the same residence in Luxembourg.

Updated on: 29/10/2025