There are several ways you can schedule a free appointment to get tested for Covid-19. You can call the toll-free number 0800 1202 (or +31 850 659 063 if you’re calling from a foreign phone). Or you can schedule an appointment online here. Note that in order to schedule an appointment online you require a DigiD.
For any questions related to scheduling a free test in the Netherlands, please visit the Government’s website
Answers to questions about Covid-19 testing outside of the Netherlands can be found here