Who can complete Form 166?

Residents and cross-borders who wish to change their withholding tax status.

Here are a few examples:

• A married cross-border couple who wish to apply for a fixed rate (equivalent to tax class 2 for married cross-border ).
• A cross-border couple who wish to revoke collective taxation (fixed rate) and revert to the ordinary law system (tax class 1).
• A resident couple who wish to opt for collective taxation (tax class 2)
• A cross-border couple who wish to adapt their fixed tax rate following a change in their income.

Updated on: 15/07/2025