You should do these actions
1. Install/activate plugin https://wordpress.org/plugins/woocommerce-eu-vat-assistant/
2. Visit >WooCommerce>Phone Orders>Settings>Customers and mark checkbox "Show field "VAT Number"
3. Add following PHP code to functions.php(child theme!) OR using plugin https://wordpress.org/plugins/code-snippets/
// Before using this code you must // - install https://wordpress.org/plugins/woocommerce-eu-vat-assistant/ // - mark "Show field Vat Numbe" in >Phone Orders>Settings>Customers add_filter( 'wpo_after_update_customer', function($customer, $request ){ if($customer['custom_fields']['vat_number'] AND class_exists("Aelia\WC\EU_VAT_Assistant\EU_VAT_Validation") ) { $vat_number = $customer['custom_fields']['vat_number']; $customer_country = substr($vat_number,0,2); $shop_country = WC_Countries::get_base_country(); $validation = Aelia\WC\EU_VAT_Assistant\EU_VAT_Validation::factory(); $raw_vat_validation_response = $validation->validate_vat_number($customer_country, $vat_number); if($raw_vat_validation_response['valid'] == true) { /* An EU customer will be considered exempt from VAT if: * - He is located in a country different from shop's base country. * - He is located in the same country as the shop, and option "remove VAT * when customer in located in shop's base country" is enabled. */ if( ($customer_country != $shop_country) || Aelia\WC\EU_VAT_Assistant\WC_Aelia_EU_VAT_Assistant::settings()->get(Aelia\WC\EU_VAT_Assistant\Settings::FIELD_REMOVE_VAT_IF_CUSTOMER_IN_BASE_COUNTRY) ) { $customer['is_vat_exempt']= true; } } else { $customer['is_vat_exempt']= false; //rebuld HTML, mark in red $customer['formatted_billing_address'] = preg_replace( '#>Vat number: (.*?)<#s', '>Vat number: <span class="wpo_custom_field required-field">' . $customer['custom_fields']['vat_number'] . '</span><', $customer['formatted_billing_address']); } } return $customer; },10,2);