Remove Purchase Order field from Wholesale checkout page, see plugin https://stephensherrardplugins.com/plugins/woocommerce-wholesale-ordering/. Why is it there, plugin developer: At least here is the USA most companies that order wholesale from their vendors, have their own internal Purchase Order numbers that they assign to each order they mak…

functions.php

// Remove Purchase Order field from Wholesale checkout page, see https://gist.github.com/Willem-Siebe/f23e348d1165d7934868.

function wsis_remove_purchase_order_field($fields) {
    if (isset($fields['order']['purchase_order'])) {
        unset($fields['order']['purchase_order']);
    }
    return $fields;                
}
add_filter( 'woocommerce_checkout_fields', 'wsis_remove_purchase_order_field', 15, 1);