OPay Cashier API
The OPay Cashier API is the primary merchant payment API behind OPay Checkout. It exposes a hosted Express Checkout endpoint (cashier/create returning a cashierUrl), server-to-server payment creation for 3DS bank cards, bank transfer, bank USSD, bank account, POS, OPay wallet QR, and reference code payments, plus status queries, cancel, refund, and refund-status operations. Authentication uses an Authorization Bearer token — the public key for cashier/create and an HMAC-SHA512 signature over the JSON body (signed with the merchant's private key) for all other endpoints — along with a MerchantId header.
Documentation
Documentation
https://documentation.opaycheckout.com/
GettingStarted
https://documentation.opaycheckout.com/getting-started
Authentication
https://documentation.opaycheckout.com/payment-authentication
APIReference
https://documentation.opaycheckout.com/server-apis-overview
Specifications
Other Resources
Webhooks
https://documentation.opaycheckout.com/payment-notifications
Sandbox
https://testapi.opaycheckout.com/api/v1/international
Production
https://liveapi.opaycheckout.com/api/v1/international
Errors
https://documentation.opaycheckout.com/error-codes
SignatureCalculator
https://documentation.opaycheckout.com/signature-calculator