You may receive a letter from the CAK. You must respond to this. This letter is sent because they are investigating whether all residents in the Netherlands have health insurance. You are required to have health insurance if:

• You are a Dutch citizen and over 18 years old.
• You have another nationality, but you work in the Netherlands.

If you live in the Netherlands, but have another nationality and do not work in the Netherlands, you can file an objection with the CAK. For this, you need to fill out the SVB form (Investigation Insurance WLZ). Once you have done this, the CAK will investigate whether you indeed do not need Dutch health insurance. The form can be downloaded here: https://www.svb.nl/Images/3299NT.pdf