Every working morning, tens of thousands of people cross a border to reach their desks in Luxembourg. They live in France, Belgium or Germany, where life is cheaper, and they earn in a country where salaries are high. The system is generous but it has traps, and they are mostly counted in days. This guide covers cross-border workers in Luxembourg: tax, remote work, social security and unemployment.
What counts as a cross-border worker in Luxembourg?
A cross-border worker lives in one country and works in Luxembourg. For tax purposes, that makes you a non-resident of Luxembourg. In principle you are taxed there only on your Luxembourg income, and the tax convention between Luxembourg and your country of residence decides how the rest is treated. Luxembourg does not have a special "frontalier status" like the one that exists between France and Switzerland: the bilateral conventions apply.
How many remote-work days are you allowed?
This is the number everybody asks about. Luxembourg's tax administration (ACD) states a 34-day tolerance threshold for residents of three neighbours:
- France: 34 days from 2023 (it was 29 days up to 2022);
- Belgium: 34 days from 2022 (24 days up to 2021);
- Germany: 34 days from 2024 (19 days up to 2023).
While you stay within it, Luxembourg keeps the right to tax your whole salary. Once you exceed it, Luxembourg loses the right to tax the salary for the work done outside its territory, which then becomes taxable in your country of residence, and you get two tax files to manage. For Belgium and Germany, the ACD specifies that this covers every day worked in your country of residence from the first one, not only the days above 34. All working days count, including part-time days and shortened days. The threshold applies to other professional stays abroad as well, such as business trips and training, not just remote work.
The ACD's FAQ, read in October 2026, announces no change for 2026. For France, the ACD published on 24 June 2026 a circular (L.G.-Conv. D.I. n° 61) on how the 34-day threshold is applied, replacing the one of 2020. If you live in France, read it, or have it explained by an adviser, before planning your year.
Who can be taxed like a resident?
A non-resident can ask for assimilation to a resident, and then benefits from a resident-style tax class, if one of these conditions is met:
- at least 90% of the worldwide income is taxable in Luxembourg; or
- foreign income that is not taxable in Luxembourg is below €13,000; or
- for residents of Belgium, more than 50% of the household's professional income is taxable in Luxembourg.
Guichet.lu says the option goes through the return (modèle 100) and covers worldwide income, which is used to compute your rate, not to tax foreign income in Luxembourg. The first 50 days of salaried work abroad count as Luxembourg-taxable for the 90% calculation. For a couple, the 90% test is applied to each spouse separately, according to the ACD. Tax returns are due by 31 December of the year after the tax year. Non-residents who are not taxed by assessment can also ask for an annual adjustment (form 163 NR) under conditions, such as nine months of continuous work in Luxembourg.
Counting days, choosing between assimilation and the default treatment, and keeping two tax authorities consistent is a lot to do alone. Moovy can lay out the official rules for your country of residence and help you prepare the questions to bring to a tax adviser. It gives guidance, not a tax opinion.
What about social security when you work from home?
Tax and social security are two separate regimes, and people often confuse them. The CCSS explains that since 1 July 2023 a European framework agreement can apply when teleworking from the country of residence makes up 25% to under 50% of total working time. Below 25%, the usual EU coordination rules apply. From 25% upward, the agreement allows you to stay in the Luxembourg system, but only if both countries are signatories, the telework takes place only in your country of residence, you can connect to your employer's IT systems, you have no other activity in your country of residence or elsewhere, and your employer declares it to the CCSS with its online form. Self-employed workers and non-EU nationals are excluded from the agreement. At 50% or more, your residence country may become responsible. The CCSS page dates from 2023, so ask the CCSS whether anything has changed before you rely on it.
Remember that the 34-day tax limit and the 25% social-security limit are different numbers. Staying under one does not protect you under the other.
Who pays if you lose your job?
For a cross-border employee, the competent body of the country of residence pays unemployment benefit, not the ADEM, and its own rules set the amount and the duration. You register and claim with the employment body at home (France Travail in France, the Bundesagentur für Arbeit in Germany, the competent body in Belgium). Your last Luxembourg employer fills in a work certificate, from which the ADEM issues the U1 form that records your Luxembourg employment periods and sends it to your home address. Read the ADEM's page for frontaliers before you leave a job so you do not miss a step.
Should you move to Luxembourg or keep commuting?
It is a trade-off of rent against time. Housing in Luxembourg is far more expensive than across the border, as the official housing observatory shows: in 2025 the median asking rent for an apartment was €33 per square metre in Luxembourg, against about €12 in the northern Lorraine and about €10 in Wallonia, Rhineland-Palatinate and Saarland. But a move changes your tax residence, your class, your commute and your family's schooling. We compare both in cost of living in Luxembourg, and the moving checklist is in the guide to moving to Luxembourg.
What mistakes cost cross-border workers money?
- Exceeding the 34 days without noticing. Keep a calendar of days outside Luxembourg.
- Assuming remote work is invisible to the CCSS. Regular telework needs a declaration.
- Forgetting the 150 km rule. If you lived near the border, you cannot use the impatriate regime when you move; see income tax in Luxembourg.
- Missing the 31 December deadline for the return that carries your assimilation request.
How do you keep track of your days as one of the cross-border workers in Luxembourg?
The 34-day figure is simple; proving it is not. Treat it like an expense account. Keep a calendar, shared with your employer if possible, marking every day you work outside Luxembourg: remote days at home, a client visit across the border, a training course abroad. Mark part-time days too, because all working days count. Keep emails, agendas and travel tickets that back it up. If you are ever asked to explain a year, a clean record is your best defence.
Agree the rules with your employer in writing. Some employers set their own, lower limits, and your contract or a company policy may say more than the tax threshold does. If you are asked to work from home regularly, ask who will declare it to the CCSS and when.
Which authorities do cross-border workers in Luxembourg deal with?
Quite a few, and it helps to keep them straight.
- The ACD (Luxembourg tax administration) for your tax card, return and assimilation request.
- Your home tax office for your own return and the treaty credit.
- The CCSS for social security and the telework declaration.
- The employment body of your country of residence for unemployment.
- The ADEM for the Luxembourg certificates used in these procedures.
Do not wait until something goes wrong to find out which one answers which question.
Conventions and thresholds change. Before you accept a remote-work arrangement or choose assimilation, have a tax adviser who knows both Luxembourg and your country of residence check your case: the two tax files have to match.