<?php
// Do NOT include the opening php tag shown above. Copy the code shown below.

add_action( 'woocommerce_after_order_notes', 'wpdesk_vat_field' );
/**
* VAT Number in WooCommerce Checkout
*/
function wpdesk_vat_field( $checkout ) {
    echo '<div id="wpdesk_vat_field"><h2>' . __('VAT Number') . '</h2>';

    woocommerce_form_field( 'vat_number', array(
        'type'          => 'text',
        'class'         => array( 'vat-number-field form-row-wide') ,
        'label'         => __( 'VAT Number' ),
        'placeholder'   => __( 'Enter your VAT number' ),
    ), $checkout->get_value( 'vat_number' ));

    echo '</div>';
}