What does the warning message about the assimilation of resident taxpayers mean and what should I do?

The assimilation alert message appears on your account when the system detects that you do not automatically meet the criteria to be considered a Luxembourg tax resident. This information is important because assimilation status has a direct impact on your taxation: it determines your entitlement to certain tax deductions.

Conditions for being considered a tax resident in Luxembourg

To be considered a tax resident, you must meet at least one of the following three conditions:

• At least 90% of your household income is generated in Luxembourg.

The calculation of this percentage includes a special rule: the first 50 days worked abroad in the calendar year (e.g. teleworking) are considered as days worked in Luxembourg. This means that these days worked outside Luxembourg are ‘assimilated’ to Luxembourg income to make it easier to obtain resident status.

• The household receives less than 13,000 euros net in income from abroad (outside Luxembourg).

This condition makes it possible to assimilate taxpayers who derive the majority of their income from Luxembourg, even if they have a limited source of income abroad.

• For Belgian residents only: more than 50% of professional income is earned in Luxembourg.

This specific rule applies only to Belgian cross-border commuters, taking into account geographical proximity and bilateral tax treaties between Belgium and Luxembourg.

In the case of a married or civil union couple, it is sufficient for one of the two partners to meet at least one of these conditions for the household to benefit from assimilation.

In the event of non-assimilation

If none of the conditions are met, you will not be able to be assimilated as a Luxembourg tax resident. In this case, you will be taxed in tax class 1 (non-resident). This means that you will not be able to benefit from the tax deductions and advantages reserved for residents, and your tax will be calculated solely on your Luxembourg-source income.

What should you do if the warning message appears even though you meet the conditions for assimilation?

If you believe you meet the criteria but the warning message remains on your account, you can contact our customer support team:

• By email: help@taxx.lu
• Or via online chat.

Our teams will be able to check your situation and guide you in correcting or completing the necessary information.

Updated on: 31/10/2025