When should I complete Form 100?

You must complete form 100 when :

the household's taxable income exceeds €100,000 per year

in the event of multiple remunerations when taxable income exceeds €36,000 for taxpayers in tax classes 1 and 2 and €30,000 for taxpayers in tax class 1a.

for Luxembourg non-residents, when you are taxed at a flat rate.

Or if your taxable income in Luxembourg is not subject to withholding tax, such as for :

• income from the exercise of a liberal profession
• income from the rental of real estate
• income from salaries paid by a foreign employer or pensions paid by foreign pension funds
• taxable income comprising more than 1. 500 of net income from securities subject to withholding tax
• taxable income comprising more than €1,500 of directors' fees
• spouses who are not separated, one of whom is a resident taxpayer and the other a non-resident, who have opted for joint taxation and who have provisionally obtained tax class 2 on their withholding tax form.

If you do not meet any of the above conditions and the tax authorities have not expressly asked you to submit form 100, choose form 163.

Updated on: 16/07/2025