What is a BSN number?
A BSN number (burgerservicenummer) is a citizen service number: is a unique personal registration number held by every citizen in the Netherlands. Anyone born in the Netherlands receives one automatically. When relocating to the Netherlands and staying for longer than four months, you need to apply for a BSN as soon as you arrive.
A BSN is the first step towards opening a bank account, working, applying for benefits, filing your taxes, making use of the healthcare system and so on. The government uses the number to communicate with citizens and exchange personal information quickly with other official agencies.
REGISTERING FOR A BSN NUMBER
If you want to stay in the Netherlands for more than four months, you need to make an appointment for your registration with the municipality within five days of your arrival (due to backlogs this isn't always possible so don't be concerned if you only secure an appointment a week or more after your arrival). If you have a partner and/or child(ren) who also need to be registered, they must come with you to the appointment.
Municipalities record the personal data of their residents, including marriage status, the birth of a child, or change of address in the Personal Records Database (BRP). When relocating from abroad and registering for the first time, you will receive your citizen service number (burgerservicenummer – BSN).
On the day that you register at the Gemeente, you need to be staying at a residential address that you are allowed to use to register at the Gemeente (AirBnB or holiday parks are not sufficient). If you are staying with friends or family, and they do not own their property, their landlord would need to give you written permission to use that address. Another option to consider is renting Temporary Accommodation.
If you have permission from your employer to use the company address you will need to either register with the municipality where the company address is registered or at an expat centre (this may involve a fee). You will need your employer to complete a declaration form (such as this one for the municipality in Leiden) or have them write a letter employer with the following:
a signed written declaration of consent (needs to name you and your passport number) from a representative of the company including their full name, job title, contact details and address (basically company letterhead);
If possible, company stamp;
a valid identity document (or a copy of one) for the person who signed the letter.
Not that using your company address is just temporary as it is not a residential address and is only being used for administrative reasons. You'll need to update your address to a residential address within a certain time frame - the municipality will inform you what that time frame will be.