As soon as the balance on your card is less than 0 euros, a fixed amount (10, 20 or 50 euros) is automatically charged via your bank account. You choose this fixed amount yourself when you sign up for 'automatic reload'. That way you are always ready for travel. Automatic reloading is only possible on a personal OV-chip card, not on an anonymous or disposable card. You request automatic reloading on ov-chipkaart.nl