Who can complete Form 100?

Form 100 may be completed by any person subject to tax in Luxembourg who wishes to or is required to file an annual tax return. More specifically, this applies to :

Persons who must complete form 100:

Luxembourg tax residents with worldwide income to declare (salaries, rental income, income from transferable securities, etc.).

Non-residents (cross-border commuters) who opt for collective taxation or wish to benefit from specific deductions (loan interest, life insurance, etc.).

People who receive income not subject to withholding tax or diversified income (e.g. rental income, professional income).

People who can voluntarily complete Form 100:

Any employee wishing to claim deductions or recover overpaid tax (transport costs, insurance, dependent children, etc.).

Please note:

Form 100 must be completed only once per tax household, even if you file a joint return.

The taxx.lu system can automatically tell you if you are concerned, and help you to fill in and send the right form.

Updated on: 16/07/2025