What is Form 166 used for?

Form 166 is required to request a change in your withholding tax class on your Luxembourg salary or pension.

It can be used to :

• Request collective taxation, tax class 2 or fixed tax rate (resident married couples and cross-borders)
• Apply for pure individual taxation (each partner's income and deductions are calculated separately, using tax class 1 for both.)
• Request individual taxation with reallocation (each person’s income and deductions are combined, then divided equally, 50% each, and tax class 1 is applied individually.)
• Request the revocation/cancellation of a taxation method
• Request adjustment/correction of a fixed rate (married cross-border commuters)
• Confirm the taxation method for the current tax return (this can also be done directly on form 100)

Updated on: 15/07/2025