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Not everyone in Luxembourg has to file a tax return, but many people who file voluntarily get money back. Here is who must file, the deadline, and when filing works in your favour.
In Luxembourg, tax on salaries is withheld at source. Many employees therefore have no obligation to file a tax return. But in many situations filing is mandatory – and in others it is simply very worthwhile.
The return (form 100) is mandatory in particular when taxable income exceeds certain thresholds or comes from several sources. The most common cases:
| Situation | Filing mandatory? |
|---|---|
| Annual taxable income above EUR 100,000 | Yes |
| Several salaries or pensions combined above the thresholds set by the ACD | Yes |
| Income not subject to withholding (rent, foreign income, self-employment) | Yes |
| One salary, no other income, correct withholding | No, but voluntary filing is possible |
Married couples taxed jointly and certain non-residents treated as residents must also file. If in doubt, the dedicated pages on Guichet.lu explain each case.
Since tax year 2022, the return can be filed until 31 December of the following year (for example, the return for 2025 income can be submitted until 31 December 2026). This single deadline applies to mandatory returns, voluntary returns and the annual adjustment alike.
Filing voluntarily is often worthwhile if you can claim deductible expenses: mortgage interest, insurance premiums, pension savings, childcare costs, donations. It is also attractive if you only worked part of the year in Luxembourg: monthly withholding assumes twelve months of salary, so an incomplete year often produces a refund.
Good to know: if you are not obliged to file and the calculation is not in your favour, you can simply skip the voluntary return the following year – nothing binds you permanently.
