# Callback to Merchants

## notify merchants about statuses changes

 - [POST /callback](https://docs.payconiq.be/apis/merchant-payment.openapi/callback-to-merchants/callback.md): Each merchant needs to define a specific endpoint to their backend (e.g., https://checkout.company.com/webhook/91FA6EEC30844FAAB5). This endpoint will be called by Bancontact Payconiq Company with details about the payment. This allows the merchant’s backend to process the data (mark the transaction in database, update the product count number, send email to the customer, etc.). Since webhooks are asynchronous, their order is not guaranteed.

The JSON-formatted POST request contains payment details. Bancontact Payconiq Company will sign the callback request using a JWS signature (see the specification of the Signature header for more details). In case of no response from the callback endpoint, Bancontact Payconiq Company will call the endpoint again up to three times per payment. The app must verify that:

* Notification messages originated from Bancontact Payconiq Company
* Were not altered or corrupted during transmission
* Are targeted for you
* Contain a valid signature.