Cross-border worker tax Luxembourg: who counts as "non-resident" for the ACD
The word "frontalier" is not a tax status at the Administration des contributions directes (ACD). For the ACD, someone paid in Luxembourg and living in France, Belgium or Germany is a non-resident taxpayer. Guichet.lu defines that as a person whose centre of vital interests is abroad, outside Luxembourg, according to the page on the tax withholding card for non-residents.
The status is a tax one, not a geographical one. An employee living in Thionville and another living in Lyon are both non-residents for the ACD, as long as the job is carried out in Luxembourg.
On the French side, the DGFiP says so on its page "Am I a cross-border worker?": France and Luxembourg have no special frontalier regime, and it is the tax treaty that sets where the salary is taxed. Life with two accounts and two tax offices is covered on the cross-border worker in Luxembourg page; this guide sticks to tax.
For the ACD, a frontalier is a non-resident who carries out their job in Luxembourg, nothing more.
Tax classes 1, 1a and 2: a non-resident's Luxembourg tax is settled at source
The Luxembourg employer withholds tax on every payslip, based on a tax withholding card issued by the ACD's RTS non-residents office. The card carries the tax class, and the class decides which scale applies. The three classes are described on the ACD page on tax classes for non-residents.
| Class | Who, for a non-resident | What the card shows |
|---|---|---|
| 1 | Anyone who falls in neither 1a nor 2: single people, and since 2018 married people who have not opted for assimilation | Basic individual scale |
| 1a | Widows and widowers, people who receive a tax reduction for a child, people who had completed their 64th year at the start of the tax year | Reduced individual scale |
| 2 | Married couples or partners taxed jointly, provided they meet the conditions for assimilation to a resident; divorced, legally or de facto separated and widowed people for the 3 years that follow | Couple's scale, overall rate written on the card |
The point that surprises couples: since 1 January 2018, a married non-resident receives class 1 by default and each spouse is taxed on their Luxembourg income alone, as the guichet.lu page on joint or individual taxation explains. Class 2 only comes with tax assimilation to a resident, an option exercised in the Luxembourg tax return, form 100.
The conditions for that assimilation are on the guichet.lu page on assimilation to a resident taxpayer: at least 90% of the taxpayer's income taxable in Luxembourg, or, since tax year 2018, net income not taxable in Luxembourg below €13,000. For a Belgian resident, 50% of the household's professional income taxable in Luxembourg is enough. The first 50 days worked outside Luxembourg count as Luxembourg income in this calculation.
Once assimilated, the couple chooses between joint taxation in class 2, pure individual taxation and individual taxation with reallocation. The choice produces a rate written on the withholding card and applied to every payslip. The tax class simulator puts figures on the gap between these options with your own amounts; it is an estimate for teaching purposes, not an ACD assessment.
Class 1 is the starting point for every married non-resident; class 2 is asked for, it does not come by default.
Double taxation Luxembourg-France: what the treaty prevents, and what it leaves in place
Two tax offices know about your salary. The tax treaty exists so that only one of them taxes it. For France, the treaty of 20 March 2018, consolidated by the DGFiP sets the rule in article 14: the salaries of a resident of one State are taxable only in that State, "unless the employment is exercised in the other Contracting State". What remains is what the country of residence does, and each treaty answers in its own way; the list of treaties in force published by the ACD gives the texts and their dates.
| Country of residence | Treaty with Luxembourg | What the State of residence does with the Luxembourg salary |
|---|---|---|
| France | 20 March 2018, amendments of 10 October 2019 and 7 November 2022 | Tax credit equal to the French tax (article 22): the salary enters the calculation, the credit cancels it, the other income is taxed at the rate of the total |
| Belgium | 17 September 1970, amendments up to 31 August 2021 | Exemption, with the salary taken into account for the rate on other income; a municipal tax may remain due |
| Germany | 23 April 2012, protocol of 6 July 2023 | Method set by the treaty; the consultation agreement of 11 January 2024 governs how it applies to frontaliers |
For a resident of France, article 22 provides that income taxable in Luxembourg "is taken into account for the calculation of French tax", with a tax credit equal to the amount of French tax on that income. The Luxembourg salary is therefore not taxed twice, but it weighs on the rate applied to the spouse's French salary. This is the heir of the "effective rate" of the old treaty, under a different mechanism.
The DGFiP kept the old effective rate as a tolerance for 2020 to 2023 income, then ended it. Its step-by-step guide on applying the treaty to 2024 income takes the example of Dominique, €40,000 of Luxembourg salary, and Camille, €25,000 of French salary: the €40,000 is declared gross, without deducting the tax paid in Luxembourg, in sections 1 and 6 of form 2047, then in boxes 1AF and 8TK of form 2042.
For a Belgian resident, the SPF Finances page on working in different EU member states describes the exemption: no tax is due on the exempt professional income, but that income "is taken into account to determine the rate applicable to any other income". Some treaties let a municipal tax be calculated on the exempt income.
The treaty does not remove the Luxembourg salary from the return in the country of residence; it removes the tax on it.
Remote work days for Luxembourg cross-border workers: the threshold, country by country
Each day worked from home is, strictly speaking, a day of employment exercised in the State of residence. The three treaties contain a tolerance that neutralises this count up to a certain number of days a year, according to the texts consulted in September 2026.
| Country of residence | Annual threshold | Text that sets it | Part-time |
|---|---|---|---|
| France | 34 days | Point 3 of the protocol to the treaty, raised from 29 to 34 by the amendment of 7 November 2022 | Threshold reduced pro rata |
| Belgium | 34 days | Amendment of 31 August 2021, applicable to remuneration from 1 January 2022; 24 days before that | Threshold not reduced |
| Germany | 34 working days | Article 14, paragraph 1a of the treaty as amended on 6 July 2023, applicable from 1 January 2024; 19 days before that | Threshold not reduced |
For France, point 3 of the protocol treats a resident who is at home or in a third State to work there "for one or more periods not exceeding 34 days in total" as exercising their employment in Luxembourg all year. The move from 29 to 34 days is article 1 of the amendment of 7 November 2022, reproduced in the ACD circular L.G. Conv. D.I. n° 61, for tax periods opening on or after 1 January 2023. The protocol provided for the two States to meet before 31 December 2024 to decide what comes next; the DGFiP's consolidated text, dated July 2025, still reads 34 days.
How to count is set out in the Franco-Luxembourg mutual agreement of 16 July 2020. Any fraction of a day counts as a full day, training included. Leave, weekends, public holidays and sick leave do not count. The threshold is reduced pro rata for part-time work or a contract that covers only part of the year.
Above the threshold, the tolerance falls away entirely. The State of residence "recovers the right to tax the remuneration received for employment from the first day and in proportion to the time" spent outside Luxembourg. On day 35, it is 35 days that switch to French tax, pre-filled in box 1AG according to the DGFiP step-by-step guide.
For Belgium, the ACD note on the Belgian tolerance threshold follows the same first-day logic, with no reduction of the threshold for part-time work or an incomplete year. The amendment of 31 August 2021 entered into force on 10 February 2023 and applies to remuneration for taxable periods opening from 1 January 2022.
For Germany, the ACD note on the German threshold describes the old 19-day rule, applicable until 31 December 2023. Since 1 January 2024, the consultation agreement published by the Bundesfinanzministerium on 15 January 2024 applies the "Bagatellgrenze" of 34 working days per calendar year from article 14, paragraph 1a, with no reduction for part-time work; an activity of under 30 minutes in a day does not count as a day.
Below the threshold, everything is taxed in Luxembourg; above it, each day spent at home is taxed at home, from the first one.
In retirement: the pension changes country of taxation
The salary rule does not follow the retiree. In the consolidated Franco-Luxembourg treaty, article 17 reserves pensions from past employment to the State of residence, except pensions "paid under the social security legislation", which are taxable only in the State that pays them. A pension from the Caisse nationale d'assurance pension therefore stays taxed in Luxembourg for a retiree living in France, and then enters the French calculation with the article 22 tax credit.
The DGFiP step-by-step guide on 2024 income puts these pensions in boxes 1AL and following of form 2042. A career split between two countries goes beyond this guide.
In retirement, the country of taxation depends on who pays the pension.
Frequently asked questions
Does a cross-border worker pay tax in France?
Not on the Luxembourg salary, as long as they stay under the threshold of 34 days worked outside Luxembourg: article 22 of the treaty of 20 March 2018 grants a tax credit equal to the French tax on that salary. The salary is still declared in France for its gross amount, in boxes 1AF and 8TK, and it raises the rate applied to the household's other income.
What is double taxation for a frontalier?
It is the situation where two countries tax the same salary: Luxembourg because the job is carried out there, the country of residence because the taxpayer lives there. The treaties avoid it by allocating the salary to Luxembourg and setting the other State's method: a tax credit in France, exemption with progression in Belgium.
How many remote work days can a Luxembourg cross-border worker have?
The texts in force in September 2026 set 34 days a year for a resident of France, Belgium or Germany, fractions of a day included. The French threshold is reduced pro rata for part-time work, the Belgian and German thresholds are not. Above it, the State of residence taxes every day spent outside Luxembourg, from the first one.
Which Luxembourg tax class does a married frontalier get?
Class 1 by default since 1 January 2018, with each spouse taxed on their Luxembourg income alone. Class 2 comes through the option of assimilation to a resident in form 100: at least 90% of income taxable in Luxembourg, or under €13,000 of net income not taxable in Luxembourg, or 50% of the household's professional income for a Belgian resident.
Key points
- The salary from a job carried out in Luxembourg is taxed in Luxembourg by withholding at source, whatever the municipality of residence in France, Belgium or Germany.
- The country of residence does not tax that salary a second time, but it takes it into account to set the rate applied to the household's other income.
- A married non-resident receives class 1 by default; class 2 comes through the option of assimilation to a resident, subject to the 90%, €13,000 or 50% conditions depending on the country.
- The three treaties tolerate 34 days a year worked outside Luxembourg; above that, the State of residence taxes those days from the first one.
- In retirement, a Luxembourg social security pension stays taxed in Luxembourg, while a company pension follows the country of residence.