Reorder EU VAT field on checkout page

functions.php

<?php
/**
 * Reorder EU VAT field on checkout page
 * 
 * @param $fields array The original array with the checkout fields
 * @return $fields array The updated array with the checkout fields
 * @see https://woocommerce.com/products/eu-vat-number/
 */
function smntcs_reorder_eu_vat_field( $fields ) {
	$fields['billing']['billing_vat_number']['priority'] = 35;
	return $fields;
}
add_filter( 'woocommerce_checkout_fields', 'smntcs_reorder_eu_vat_field', 11 );