Shopify makes it easy to create an order. That is not the hard part. The hard part starts when the payment does not behave like a clean, instant, single-step event. A webhook arrives twice. A payment is delayed. The amount is slightly different. The order was already cancelled. The customer says they paid, but your system still shows pending. If your integration assumes: payment_received = order_paid Enter fullscreen mode Exit fullscreen mode it will probably work in testing. It will fail in production. The real challenge is not “how to accept a payment on Shopify.” It is how to design a payment flow that stays consistent when payment events are asynchronous, duplicated, delayed, or incomplete. The Core Rule: Order State and Payment State Must Be Separate A Shopify order and an external payment are related, but they are not the same object. The order belongs to Shopify. The payment belongs to your system. If you merge them too early, you lose control.…