vat_number_checkout.php

<?php

add_action( 'woocommerce_after_order_notes', 'wpdesk_vat_field' );
/**
* Pole NIP w zamówieniu
*/
function wpdesk_vat_field( $checkout ) {

    echo '<div id="wpdesk_vat_field"><h2>' . __('Dane do Faktury') . '</h2>';
    
    woocommerce_form_field( 'vat_number', array(
        'type'          => 'text',
        'class'         => array( 'vat-number-field form-row-wide') ,
        'label'         => __( 'NIP' ),
        'placeholder'   => __( 'Wpisz NIP, aby otrzymać fakturę' ),
    ), $checkout->get_value( 'vat_number' ));
    
    echo '</div>';

}