> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cryptoprocessing.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Callbacks overview

A callback is an automatic notification sent by CryptoProcessing to your system about status changes for [deposits](/api-reference/callbacks/deposit-callbacks), [withdrawals](/api-reference/callbacks/withdrawal-callbacks), [exchange transactions](/api-reference/callbacks/exchange-callbacks), and [invoices](/api-reference/callbacks/invoice-payment-callbacks).

## Processing callbacks

Set up an HTTPS webhook endpoint where CryptoProcessing can send callbacks. Your webhook URL must use HTTPS, use a domain name, and be considered safe by VirusTotal and similar scanners.

After you create the endpoint, register it in CryptoProcessing. In your merchant settings, open the **Callbacks** tab and enter your endpoint address in the **Callback URL** field.

When CryptoProcessing sends a callback to your endpoint, your system should:

<Steps>
  <Step title="Validate the callback">
    Generate an HMAC-SHA512 signature for the callback request body using your secret key, then compare it with the value in the `X-Processing-Signature` header.
  </Step>

  <Step title="Process the event">
    Check whether the callback is a duplicate by verifying that its transaction ID has not already been processed. If it has not, process the event, for example by updating the customer’s balance in your system.
  </Step>

  <Step title="Return HTTP 200 OK">
    No response body is required.
  </Step>
</Steps>

<Note>
  For additional security, you can whitelist the CryptoProcessing IP addresses used for callback delivery. Contact Support for the current list of IP addresses.
</Note>

## Retry schedule

If your system does not respond with **HTTP 200 OK** to a callback, CryptoProcessing keeps the callback in the sending queue and retries delivery 12 times after the initial attempt.

Each retry is scheduled relative to the previous attempt: +1 minute, then +5, +15, +30, +60, +90, +120, +180, +240, +240, +240, +240 minutes.

The retry schedule is not configurable.