Cross-border worker: declaring your salary in your residence country?
Skimming?
We've prepared the shortcut for you.
This is for you if
- You live in France, Belgium, or Germany and you are an employee in Luxembourg.
- Your household has other income in your residence country: spouse's salary, rental income, investments.
- You spent more than 34 days working outside Luxembourg (in France, the threshold is lower if you work part-time or started mid-year): part of your salary is then taxable in your country (see the 34-day rule).
Not for you if you live in Luxembourg: your obligations are described in the tax guide.
Key figures to remember
| Country | Method | Where to declare | Year |
|---|---|---|---|
| France | Tax credit equal to French tax | 2047 (sections 1 and 6), then 2042 (main tax return): boxes 1AF to 1DF and 8TK | Mandatory for income received since 2024 |
| France | Days worked in France once the 34-day threshold is exceeded (all of them, from day one) | 2042: boxes 1AG to 1DG, taxable in France | Since 2023 |
| Belgium | Exemption with progression | Personal income tax return (IPP), foreign-source income | 2025 and 2026 income |
| Germany | Exemption with progression (Progressionsvorbehalt, § 32b of the German Income Tax Act, EStG) | Anlage N-AUS (schedule dedicated to foreign salaries) | 2025 and 2026 income |
| Germany | Mandatory return if a German salary subject to withholding tax coexists with more than €410 in income subject to Progressionsvorbehalt (threshold specific to this case, not a general rule) | § 46 EStG | Law in force in 2026 |
How to declare your Luxembourg salary
Gather your Luxembourg amounts
Collect your annual salary certificate and your December payslips. Also note down your days worked outside Luxembourg: they determine the portion taxable in your residence country.
In France: form 2047 then return 2042
According to the 2025 income instructions 2047 (ouvre dans un nouvel onglet), you enter your salary in section 1 and section 6 of form 2047, then in box 1AF (1BF for declarant 2) and box 8TK of form 2042. The amount is declared without deducting the tax paid in Luxembourg, and without applying the 10% deduction yourself, which is calculated automatically.
In Belgium: complete IPP tax return
The Federal Public Service (FPS) Finance requires you to declare all your worldwide income, even if exempt by treaty (FPS Finance (ouvre dans un nouvel onglet)). If you receive a simplified tax proposal without your foreign income, do not confirm it: submit a complete return.
In Germany: Anlage N-AUS
Salary exempt under the tax treaty is declared in Anlage N-AUS, the schedule used to calculate this exempt salary (2025 ELSTER guide (ouvre dans un nouvel onglet)). Germany only exempts it if it was actually subject to tax in Luxembourg, i.e. included in the Luxembourg tax base (circular of the Direct Tax Administration, ACD, No. 71 of 18 March 2024).
Keep your supporting documents
Certificates, payslips, and proof of presence in Luxembourg: your tax authority may request them, and automatic exchange of information between countries allows them to check (FPS Finance).
A worked example
Let's take Nadia and Hugo, a married couple without children living in Metz (2 tax parts). Nadia earns €40,000 in net taxable salary in Luxembourg (calculated according to French rules), and Hugo earns €25,000 in France. Tax scale applied to 2025 income (Service-public.fr (ouvre dans un nouvel onglet)):
- Income after the 10% deduction: €36,000 + €22,500 = €58,500.
- Per share: €58,500 / 2 = €29,250.
- Tax per share: (€29,250 - €11,600) × 11% = €1,941.50, i.e. €3,883 for the couple.
- No tax discount (décote): it stops at €3,277 in gross tax for a couple (Service-public.fr (ouvre dans un nouvel onglet)).
- Tax credit for Nadia's salary: €3,883 × 36,000 / 58,500 = €2,390.
- Balance to pay, on Hugo's salary: €3,883 - €2,390 = €1,493.
Without Nadia's salary, Hugo alone with 2 parts (€22,500, or €11,250 per share) would pay €0. The Luxembourg salary is not taxed in France, but it increases the household's tax from €0 to €1,493: that's what "counting toward the rate" means. Simplified trigger calculation (without other deductions or tax reductions).
Common mistakes
- Still using box 1AC (former "effective tax rate" concession): it ended for income received from 2024 onward (impots.gouv.fr).
- Declaring the salary net of Luxembourg tax: in France, it must be declared before deducting foreign tax.
- Declaring nothing because the salary is "exempt": FPS Finance reminds taxpayers that exempt income must also be declared, under penalty of fines.
- Forgetting your days worked in France once you exceed 34: they all become taxable in France from day one (boxes 1AG to 1DG), not just those beyond 34.
Frequently asked questions
No. In principle, tax treaties allocate taxing rights to Luxembourg when you work there. Your country of residence neutralizes the tax on this salary (tax credit in France, exemption in Belgium and Germany), but uses it to determine the rate applied to your other income.
In France and Belgium, yes: you declare your worldwide income (form 2047 instructions, FPS Finance). In Germany, the obligation depends on your situation (for example, a German salary in the household): your local Finanzamt (German tax office) will confirm this for you.
Belgium adds a municipal tax to income tax, the rate of which depends on your municipality. Your Luxembourg salary, exempt in Belgium, is not subject to it: a compensation mechanism compensates the municipalities. However, this tax may still be due on your other taxable income in Belgium.
No: tax assimilation only affects Luxembourg tax. Your tax return in your home country remains the same.