When you are not obliged to take out a National Health Insurance, you can, or in some cases must, arrange some other form of insurance. It is possible that based on your nationality or purpose of stay, you will still be covered under the national health insurance of your home country or a private insurance that you have taken out in your country of origin. Always make sure to check the coverage while in the Netherlands.
This may be applicable to:
Cross border workers within EEA or a treaty country: check with the SVB how you need to be insured.
Posted employees: depending on the duration of your assignment and which employer pays your salary. Contact the SVB or the national social security board in your home country for more information.
Students and non-salaried academic researchers: students under the age of 30 who are in the Netherlands for the sole purpose of studying or doing research on a (study) grant and who stay in the Netherlands for less than three years, are not considered to be residents and do therefore not fall under Dutch national social security regulations. Please note, that if you have a part-time job besides your study or research, you will have to take out a Dutch National Health Insurance.