Installing/Enabling Custom Webform Hander
A few things in addition to what @4k4 commented:

Please replace your annotation plugin reference with @WebformHandler

Use lower case / snake case names for your Webform Handler ID eg. redirect_to_ccbilling

Ensure correct directory structure where the plugin discovery will look for Webform Handler classes. This should be /modules/custom/redirect_to_ccbilling/src/Plugin/WebformHandler/RedirectToCCBillingWebformHandler.php

Ensure that your module is enabled. Either via drush en redirect_to_ccbilling -y or by enabling it on the Extend module page.


/**
 * Form submission handler.
 *
 * @WebformHandler(
 *   id = &quot;redirect_to_ccbilling&quot;,
 *   label = @Translation(&quot;Redirect to CC Billing&quot;),
 *   category = @Translation(&quot;Webform Handler&quot;),
 *   description = @Translation(&quot;Redirect user to the credit card billing page.&quot;),
 *   cardinality = \Drupal\webform\Plugin\WebformHandlerInterface::CARDINALITY_SINGLE,
 *   results = \Drupal\webform\Plugin\WebformHandlerInterface::RESULTS_PROCESSED,
 * )
 */
class RedirectToCCBillingWebformHandler extends WebformHandlerBase {