Learn › Filing taxes in Luxembourg

In short: For the 2025 tax year (filed in 2026), the forms and online services are available from 7 April 2026 and the deadline is 31 December 2026 — what counts is the date of receipt by the tax authority (Administration des contributions directes, ACD). You are notably required to file a full assessment (Modèle 100) if the household’s taxable Luxembourg income exceeds €100,000, or where several incomes combined exceed €36,000 (classes 1 and 2) or €30,000 (class 1a). Otherwise, an annual statement (Modèle 163) lets you adjust withholding that was too high. As of 2026; when in doubt, check the official sources.

Filing your tax return in Luxembourg: how it works

Kontoo editorial team · Updated 06/24/2026

In Luxembourg, tax on salaries is usually withheld at source each month. Many people are therefore not required to file a full return, but can often reclaim tax that was over-withheld. This chapter explains the difference between the full assessment (Modèle 100) and the annual statement (Modèle 163), where everything happens online, and the dates that matter. It is educational guidance, not personalised tax advice.

Check whether you are required to file a full return (Modèle 100) or whether a simple annual statement is enough.
Gather your documents: salary/pension certificates, loan interest, insurance, childcare costs, donations and other deductible expenses.
Complete your file online via the electronic assistant on MyGuichet.lu (or use the pre-filled simplified return if you received one).
Submit before the deadline and keep the acknowledgement of receipt along with your supporting documents.

What matters

The Luxembourg tax system relies heavily on withholding at source: each month, tax on salary or pension is deducted according to your tax card (tax class). At year-end, there are two situations. Either you are required to file a full return under the assessment procedure (Modèle 100) — this applies notably when the household’s taxable Luxembourg income exceeds €100,000, or when several incomes combine to more than €36,000 (classes 1 and 2) or €30,000 (class 1a). Or you are not required, in which case you can request an annual statement (Modèle 163) to adjust tax that was over-withheld. The return lets you claim deductible expenses: loan interest, insurance premiums, childcare costs, donations, work-related expenses and more. Everything now runs mainly through MyGuichet.lu, where an electronic assistant guides data entry and processing is automated. Since 2025, the ACD also sends certain eligible taxpayers a pre-filled simplified return by post, starting in late March. As of 2026; when in doubt, check the official sources.

ExampleSimplified, purely illustrative example: suppose €6,000 of tax was withheld at source from your salary over the year, but after taking your deductible expenses into account (say €4,000 of loan interest and insurance) your actual tax due is only €4,800. The annual statement or return would then show an overpayment of about €1,200 to be refunded to you. The real figures depend on the rate schedule, your tax class and your situation — this is only an illustration, not an official calculation.

Before filing, use Kontoo to gather the year’s income and deductible expenses, then create your file on the official MyGuichet.lu portal.

In depth

Pre-filled simplified return

Since 2025, the ACD sends certain eligible taxpayers a pre-filled simplified return based on the data it already holds, by post around late March. It aims to reduce the burden: check, complete and confirm. As of 2026; check your eligibility with the official sources.

Residents and non-residents (cross-border workers)

The annual statement comes in two forms: 163R for residents and 163NR for non-residents. Cross-border workers employed in Luxembourg are concerned depending on their situation (duration of activity, the assimilation option for non-resident married couples). Cross-border rules are specific — when in doubt, ask the ACD.

Why file even without an obligation

An annual statement or return often results in a tax refund thanks to deductible expenses not reflected in the monthly withholding. This is especially true after a mid-year change (marriage, a child, a property loan, partially worked months).

Checklist

I know whether I must file a full return (Modèle 100) or whether an annual statement is enough.
I know the filing window for 2026: from 7 April to 31 December 2026.
I have gathered my income certificates and supporting documents for deductible expenses.
I know that the return is filed online on MyGuichet.lu.

Common myths

Myth: Because tax is withheld at source, I never have to do anything.

Reality: False. Even without a filing obligation, an annual statement can refund an overpayment. And above certain thresholds, the full return is mandatory.

Myth: As long as I send my return before 31 December, I am on time.

Reality: Be careful: it is the date of receipt by the ACD that counts, not the date you send it. Better to file early, especially online.

Frequently asked questions

What is the deadline for 2026?

For 2025 income, the return can be filed from 7 April to 31 December 2026. It is the date of receipt by the ACD that counts, not the date you send it. As of 2026; when in doubt check impotsdirects.public.lu.

What is the difference between the return and the annual statement?

The full assessment (Modèle 100) is the complete taxation, mandatory above certain thresholds. The annual statement (Modèle 163R for residents, 163NR for non-residents) is a simpler, on-request procedure to reclaim withholding tax that was too high when you are not required to file the Modèle 100.

Where do I file my return?

Online via the electronic assistant on MyGuichet.lu, which is processed automatically. A pre-filled simplified return is also mailed to certain eligible taxpayers from late March 2026.

All lessons · Glossary · Editorial · Kontoo does the math and explains – this is general education, not tax, legal or financial advice.

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