Cross-border work in Luxembourg
Nearly half of Luxembourg's workforce commutes from France, Belgium or Germany. The rules differ by country.
Approximately 47% of Luxembourg's workforce are cross-border workers, the highest share in the European Union and a defining feature of the country's labour market. The bulk arrive from France (around 125,000, mostly from the Moselle and Meurthe-et-Moselle), Belgium (around 52,000, mostly Province de Luxembourg and surroundings) and Germany (around 50,000, mostly Rhineland-Palatinate and Saarland). The framework that governs how they are taxed, insured and entitled to family benefits is a stack of three layers: the bilateral tax convention with each country; EU regulation 883/2004 on social-security coordination; and a multilateral framework agreement on telework negotiated between 2023 and 2024 that loosened the social-security threshold for participating countries (France, Belgium and Germany were all signatories at the time of writing — verify current status with your CCSS contact).
Tax is generally paid in Luxembourg under those bilateral conventions, with each country setting its own tolerance for the number of days a resident can work outside Luxembourg before the home country starts taxing those days. Social security is separate: it stays with Luxembourg as long as you perform less than 25% of your work in your country of residence, raised to up to 49.99% under the framework agreement on telework. The two thresholds are independent — a fact that catches out almost every cross-border worker who tries to manage them as if they were the same.
The three country guides
Each border has its own convention, train lines and quirks. Start with the country you live in — or are thinking of living in.
From France
The 2023 amended convention, the remote-day tolerance, the Thionville–Metz train corridors, and what counts as a "working day" for French tax purposes.
From Belgium
The BE-LU framework, the IPP declaration codes, additionnels communaux, and the Arlon–Athus–Aubange train routes most Belgian commuters take.
From Germany
The DE-LU framework's stricter remote-day rule, the Kirchensteuer trap, the Trier corridor, and how Anlage N-AUS reports a Luxembourg salary back to the Finanzamt.
Cross-border tax framework
Cross-link: how the bilateral conventions, day thresholds and EU 883/2004 interact at the level of principles, written from the Luxembourg tax angle.
What's covered in this topic
The four ideas that drive every cross-border question. The country guides build on these.
Tax framework
Bilateral conventions FR-LU, BE-LU and DE-LU govern where employment income is taxed. The principle is "work state" — but each convention sets its own tolerance for days worked elsewhere.
Social security
EU regulation 883/2004 anchors affiliation to the work state if you perform less than 25% of your activity in your residence country; the multilateral framework agreement on telework raises that to 49.99% for signatories.
Remote-work day thresholds
Each bilateral convention has its own count: France, Belgium and Germany have all renegotiated theirs in the last few years. Numbers move — always verify against the current avenant.
Filing in two countries
Luxembourg taxes at source via the payroll; the residence country still requires a declaration of foreign income, applies the convention reduction, and reconciles. France 2042+2047, Belgium IPP, Germany Anlage N-AUS.
Related guides across the site.
Working in Luxembourg, living in France
The 2023 avenant, the day-count rule, train lines, formulaire 2042 + 2047 and the CAF coordination question.
Cross-borderWorking in Luxembourg, living in Belgium
The IPP codes, the additionnels communaux trap, Arlon and Athus train lines, family allowance coordination.
Cross-borderWorking in Luxembourg, living in Germany
Anlage N-AUS, the Kirchensteuer trap, the Trier and Saar corridors, Kindergeld coordination via the Familienkasse.
TaxCross-border tax: FR, BE, DE
Day thresholds, social-security framework, filing in two countries — written from the Luxembourg tax angle.
WorkReading a Luxembourg payslip
CCSS, FNS, dependency contribution and the tax retained at source — line by line, with the cross-border non-resident column.
HousingNeighbourhoods & commuter towns
Where the LU-based commute from Thionville, Arlon and Trier actually lands you in real travel time — by P+R or train.
Cross-border — frequently asked.
Six questions that come up at the first contract negotiation. Each links to the full country guide.
How many days can I telework from home?
The tolerance is country-specific. France, Belgium and Germany each renegotiated their bilateral convention in the past few years, and the day-count is set by the current avenant. Once you exceed it, the home country can tax the share of salary corresponding to days worked at home. Verify the current threshold for your country before signing a remote-work agreement. France → · Belgium → · Germany →
Do I file a tax return in both countries?
In practice yes. Luxembourg taxes the employment income at source; your country of residence still wants a declaration of foreign income to apply the convention reduction or exemption and to assess things like local surcharges, means-tested benefits and joint-filing maths with a spouse. France: formulaire 2042 + 2047. Belgium: IPP with cross-border codes. Germany: Anlage N-AUS. The framework, in detail →
Where do I pay social security?
Under EU regulation 883/2004 you are affiliated where you physically work — Luxembourg, via the CCSS — as long as less than 25% of your activity is performed in your country of residence. The multilateral framework agreement on telework raises that to up to 49.99% for participating countries. Above the threshold, social security shifts to the residence country, with implications for healthcare, pensions and unemployment. Social-security side of the framework →
Can I keep my home-country pension?
Yes. EU coordination preserves rights accrued in each country. At retirement each system pays its own pro-rata pension based on the years contributed there. Most long-term cross-border workers end up with two parallel pensions: the Luxembourg CNAP for the LU career years, plus the French CNAV, the Belgian Service fédéral des pensions or the German DRV for the years contributed before or after. Work pillar →
What if I move my residence to Luxembourg?
You become a Luxembourg tax resident, taxed on worldwide income, and you gain access to the full resident tax classes including the joint or individual filing options for married couples. Social-security continues with the CCSS as before. Cross-border status simply ends. You register at your commune within three months. From that point onwards you file only in Luxembourg. First 90 days →
Is the convention threshold the same as the social-security one?
No, and this is the single most common source of confusion. The convention threshold is in days and is set bilaterally by each tax treaty (FR-LU, BE-LU, DE-LU). The social-security threshold is in percentage of working time and is set by EU 883/2004 (25%) plus the multilateral framework agreement on telework (up to 49.99%). It is entirely possible to exceed the tax threshold while remaining safely under the social-security one, or vice versa. Worked-through example →
Cross-border life sits on top of three other topics
The cross-border framework cannot be understood in isolation. The tax side is the Luxembourg-flavoured half of a two-country picture that is dealt with from the LU angle in the cross-border tax guide; the LU-side payslip explanation in reading a Luxembourg payslip applies identically to cross-border workers (the gross is the same, only the personal income-tax column changes). The decision of whether to stay a frontalier or move into Luxembourg is also a housing question — see the neighbourhoods guide for the realistic comparison between commuting from Thionville or Arlon and renting near Kirchberg. And the family-benefits coordination — France's CAF, Belgium's FAMIRIS / Iriscare, Germany's Familienkasse — is summarised in family & schools.
Three things are worth saying about how this topic ages. First, the bilateral conventions are amended every few years, often by avenant, and the day-counts change with each amendment — figures on this site marked [verify] should always be checked against the current text. Second, the framework agreement on telework is opt-in by country; if a signatory withdraws, the social-security ceiling for that border drops back to the 25% default. Third, the political climate matters: France in particular periodically signals dissatisfaction with the share of Luxembourg payroll tax it forgoes, which sometimes feeds into compensation discussions across the border. None of this affects the practical answer to "where do I file?" — it affects the size of the practical answer over time.
Three borders, three frameworks. Decoded from the conventions, not the LinkedIn summary.
Every cross-border page on World.lu cites the bilateral convention, the EU regulation 883/2004 article, the framework agreement on telework and the residence-country form (formulaire 2042, IPP, Anlage N-AUS). Day-count thresholds move — they are flagged [verify] on every page so you confirm against the current source before signing a remote-work agreement.