Ratepay Payment API Ratepay Auth API Merchant Backend Merchant Frontend Customer Ratepay Payment API Ratepay Auth API Merchant Backend Merchant Frontend Customer Required for risk and fraud scoring All write operations are idempotent (authorize, capture, cancel, refund) opt [OTP requested by Ratepay] loop [Retry authorization max 3 attempts] alt [Hard risk decline] [Soft decline] alt [Authorization approved] [Authorization declined] Time passes - order processing and shipment Invoice creation and customer communication Supports partial captures, cancels, refunds Open checkout 1 Render checkout and Ratepay payment options 2 Select Ratepay payment method 3 Device fingerprinting 4 Customer consent for terms and risk check 5 Click Buy now 6 Buyer basket payment and device data 7 OAuth token request 8 Bearer token 9 POST /transactions authorize 10 Authorization pending [OTP required] 11 Request one-time passcode 12 Display OTP input 13 Enter OTP code 14 OTP code 15 POST /verify confirm (OTP) 16 OTP verification result 17 Approved or declined 18 Proceed with order 19 Show fallback payment methods 20 Adjust data 21 POST /transactions authorize 22 Approved or declined 23 Final decline after retries 24 POST /captures after shipment 25 Capture confirmed 26 Shipping information optional 27 POST /cancellation optional 28 Cancellation confirmation 29 POST /refunds optional 30 Refund confirmation 31