Customize the "Invoicing with InvoiceXpress for WooCommerce" VAT field

ivoicexpress_vat_field_woocommerce.php

<?php
//We hook woocommerce_checkout_fields at 50, so this needs to be at least 51
add_filter( 'woocommerce_checkout_fields', 'ix_vat_woocommerce_checkout_fields', 51 );
function ix_vat_woocommerce_checkout_fields( $fields ) {
	//Change label - originally __( 'VAT number', 'woo-billing-with-invoicexpress' )
	$fields['billing']['billing_VAT_code']['label'] = 'My VAT label';
	//Change priority - originally 120, 31 is after company
	$fields['billing']['billing_VAT_code']['priority'] = 31;
	//Make it half size and on the left
	$fields['billing']['billing_VAT_code']['class'] = array( 'form-row', 'form-row-first' );
	return $fields;
}