Filing a tax return is an important annual step for every taxpayers, whether they are Luxembourg residents or cross-border workers. In many cases, it is not mandatory (due to withholding tax) but is often beneficial. In 2025, several changes and tax relief measures come into effect, simplifying the process for many taxpayers. Here is a comprehensive guide to help you complete your tax return with ease.
Steps and deadlines for filing your tax return
- Receiving the form: forms and online services will be available from 7 April 2025 on MyGuichet.lu. If you do not receive a paper form or an online filing invitation, you can still submit your tax return.
- Gathering necessary documents: ensure you have all supporting documents related to your income and deductible expenses (for example, the "Wage Statement" provided by the employer in the first quarter of the current year).
- Completing the Model form 100: this form is essential for declaring your income and benefiting from possible tax deductions.
- Submitting your tax return: it is essential to ensure that the declaration is submitted before 31 December 2025.
- Tax calculation: the tax administration will determine the amount of tax you owe based on your income, deductible expenses, and family situation.
Filing methods
- Paper version: fill in the form provided by the tax authorities and submit it to your tax office or send it by post;
- Online: use the MyGuichet.lu portal for a faster and easier process (log in using LuxTrust or GouvID or eIDAS).
Penalties
- Late submissions will result in penalties and interest charges (fine of up to €25,000, a tax surcharge of 10% to 20% depending on the delay);
- Extensions may be requested if necessary;
- Online filing allows for faster processing, with tax calculations available within 15 days.
Key tax changes in Luxembourg for 2025
Several important tax changes apply to the 2025 tax return:
- Postponed start date: tax return submissions will exceptionally begin on 7 April 2025 instead of the usual first Monday of February;
- Pre-filled tax returns for simple cases: the Luxembourg Inland Revenue will introduce a system for certain taxpayers with easy tax situations, whether they are residents or cross-border workers;
- Adjustment of the tax scale: a reduction equivalent to 2.5 index brackets, reducing the tax burden on households;
- Tax exemption for single-parent families: families with an annual income of up to €52,400 will be exempt from tax;
- Increase in the single-parent tax credit (CIM): the CIM will increase from €2,505 to €3,504;
- Young Employee bonus: a 75% tax exemption on a bonus ranging from €2,500 to €5,000 will be granted to young workers under 30 signing their first employment contract;
- Tax credit for overtime (CIHS): can amount to up to €700 per year for certain cross-border workers;
- Eased tax regime for impatriates: aims to enhance Luxembourg’s attractiveness for highly qualified workers.
Discover what's new in the job market in 2025.
By following these guidelines, whether you are a Luxembourg resident or a cross-border worker, you can ensure an optimal tax declaration process and avoid any fiscal inconveniences.
Want to easily generate your tax return? Taxx.lu is an online platform designed to simplify tax filing for individuals in Luxembourg. Paid service: €59.
For more details or any specific questions, please refer to the Frontaliers.lu tax guide.
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