Disables sending a invoice emails for check orders whenever an order is saved in success status.

disable_pmpropbc_send_invoice_email.php

<?php

/**
 * Disables sending a invoice emails for check orders whenever an order is saved
 * in success status.
 * 
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

function my_disable_pmpropbc_send_invoice_email() {
	remove_action( 'pmpro_updated_order', 'pmpropbc_send_invoice_email', 10, 1 );
}
add_action( 'init', 'my_disable_pmpropbc_send_invoice_email' );