What is Checkbook.io? March 29, 2021 17:47 Updated Checkbook.io is a secure payment solution that provides you with an easy and secure way to receive online payments. Related articles When will I be paid? I haven’t received my payment, what do I do? What if I disagree with the amended offer after my electronics have been evaluated by Backflip? How do I prepare my device for Backflip? Can I change my payment method?