Applying for a 'BSN'
The Citizen Service Number (burgerservicenummer, BSN or ‘Sofinummer’) is the personal code with which you are registered with the government. Although you are not officially required to apply for a BSN, it could be handy to have one for practical reasons. For example, it would allow you to open a Dutch bank account.
If you will be staying for less than four months, you can apply to the tax office (Belastingdienst) for a BSN. If you would like, the International Office can make an appointment for you in order to request a BSN.
If you will be staying longer than four months, a BSN will automatically be sent to your home address. This number is issued by the municipality in which you will be living once you have registered. Your personal BSN will be sent to your home address about 10 days after registration.