Hook um_before_submit_form_post

um_before_submit_form_post.php

<?php

/**
 * Hook: um_before_submit_form_post
 *
 * Type: action
 *
 * Description: Fires on the form submit before validation.
 *
 * @example https://github.com/ultimatemember/ultimatemember/blob/master/includes/core/class-form.php#L424
 * @link    https://docs.ultimatemember.com/article/1063-umbeforesubmitformpost
 *
 * @package um\core
 * @see     um\core\Form::form_init()
 * @since   2.0
 * @version 3.0
 */
function my_before_submit_form_post() {
	// your code here.
}
add_action( 'um_before_submit_form_post', 'my_before_submit_form_post', 10 );