A simple GST line itemizer for the Event Espresso 3 invoice template function file. Works in conjunction with https://gist.github.com/joshfeck/e2b91cd6599000ecb772

add-GST-to-invoice.php

<?php
//* Please do NOT include the above opening php tag

function my_itemised_surcharge( $attendees ){
	$options = get_option( 'events_organization_settings' );
	$currency = $options['currency_symbol'];
	$this->SetFillColor( 239,239,239 );
	
	// pull the selected ticket price breakdown from the database 
	global $org_options;

	$total_price_per = $attendees[0][0][2];
	
	// In this case GST is 10 percent of the total, multiplier of 10/11
	$price_before_gst = $total_price_per * .909090909;
	
	$gst = $total_price_per - $price_before_gst;
	
	// print unit price w/o surcharge
	$this->Cell( 95, 7, __( 'Price per unit excluding GST:','event_espresso'), 0, 0, 'L', true );
	$this->Cell( 90, 7, html_entity_decode( $currency, ENT_QUOTES, 'ISO-8859-15' ) . number_format( $price_before_gst,2, '.', '' ), 0, 1, 'C', true );
	
	// print unit surcharge
	$this->Cell( 95, 7, __( 'GST per unit:','event_espresso' ), 0, 0, 'L', true );
	$this->Cell( 90, 7, html_entity_decode( $currency, ENT_QUOTES, 'ISO-8859-15' ) . number_format( $gst,2, '.', '' ), 0, 1, 'C', true );
}