Hook um_add_error_on_form_submit_validation

um_add_error_on_form_submit_validation.php

<?php

/**
 * Hook: um_add_error_on_form_submit_validation
 *
 * Type: action
 *
 * Description: Fires on the form validation before adding an error message.
 *
 * @example https://github.com/ultimatemember/ultimatemember/blob/master/includes/core/um-actions-form.php#L575
 * @link    https://docs.ultimatemember.com/article/974-umadderroronformsubmitvalidation
 *
 * @package um\core
 * @see     um_submit_form_errors_hook_()
 * @since   2.0
 * @version 3.0
 *
 * @param array  $field Field data.
 * @param string $key   Field key.
 * @param array  $args  Form arguments.
 */
function my_add_error_on_form_submit_validation( $field, $key, $args ) {
	// your code here.
}
add_action( 'um_add_error_on_form_submit_validation', 'my_add_error_on_form_submit_validation', 10, 3 );