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description: Online Payment / Transaction Process
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# Online Payment / Transaction Process

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<figure><img src="https://lh7-rt.googleusercontent.com/docsz/AD_4nXd1_GNnvc6LMRttkfQRYyIOyYeLVD8d9JTOteluwW4XL6028fxL39GIagbZD62HTqj3JgjukbXaAXlQ3gwywaiYhEd3-gezoGnpsucsdRrVllYLdVlJgKlE5EahcmyCtBlm2A9pQ-LXUOo8No73d4MHWvs-vny25t7yNX-AK8CMAOWSbN9qFCg?key=YOQU3AbjLOhXrKaT0sW92g" alt=""><figcaption></figcaption></figure>

**Merchant needs to prepare 3 simple and similar payment endpoint scripts** to handle the payment notification from the payment gateway:

1. **Return URL:** front-end or browser redirection notification, which are normally not a 100% reliable and robust channel due to unexpected network connectivity issue or client-side behavior, such as browser application crashes;
2. **Notify URL (webhook):** a server-to-server back-end webhook which is more robust and crucial for payment status or order update;
3. **Callback URL (webhook):** a special handler webhook to get notified on non-realtime payment status, such as “deferred status update”, change of payment status, or Fiuu Cash, which is not a realtime payment naturally.



**After the normal payment flow,** merchants can always send payment status query requests, which is defined in reQuery APIs (a.k.a PSQ, Payment Status Query).

<figure><img src="https://lh7-rt.googleusercontent.com/docsz/AD_4nXdB2zEtCbOIIxbv6_rQHnwqfLt_ofwKV6HMMN-HtIUkjmNE79d194Ysub_LjxqDquKhXaQrqEbYoYih_xxzw-bCmmb0nFA9e25aXRKmuionwFmooMAcV38zDTJljx2fFS0Xq0K28z4A0K-ItotzFQlnyBqMV2NckkHU0zTqojaSI_uGH3Wik2k?key=YOQU3AbjLOhXrKaT0sW92g" alt=""><figcaption></figcaption></figure>



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