Add subtotal (!!invoice_subtotal!!) and tax (!!invoice_tax!!) variables to email templates

my_pmpro_add_order_details_to_email.php

<?php // copy from below
/**
 * Add !!invoice_subtotal!! and !!invoice_tax!! variables to email templates where an Order ID is available.
 *
 * 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_pmpro_add_order_details_to_email( $data, $email ) {

	if ( isset( $data['order_id'] ) ) {
		$order = new MemberOrder( $data['order_id'] );
		$data['invoice_subtotal'] = isset( $order->subtotal ) ? pmpro_formatPrice( $order->subtotal ) : '';
		$data['invoice_tax'] = isset( $order->tax ) ? pmpro_formatPrice( $order->tax ) : '';
	}

	return $data;
}
add_filter( 'pmpro_email_data', 'my_pmpro_add_order_details_to_email', 10, 2 );