protected function validate_checkout( &$data, &$errors ) {
		$this->validate_posted_data( $data, $errors );
		$this->check_cart_items();

		if ( empty( $data['woocommerce_checkout_update_totals'] ) && empty( $data['terms'] ) && ! empty( $_POST['terms-field'] ) ) { // WPCS: input var ok, CSRF ok.
			$errors->add( 'terms', __( 'Please read and accept the terms and conditions to proceed with your order.', 'woocommerce' ) );
		}

		if ( WC()->cart->needs_shipping() ) {
			$shipping_country = WC()->customer->get_shipping_country();

			if ( empty( $shipping_country ) ) {
				$errors->add( 'shipping', __( 'Please enter an address to continue.', 'woocommerce' ) );
			} elseif ( ! in_array( WC()->customer->get_shipping_country(), array_keys( WC()->countries->get_shipping_countries() ), true ) ) {
				/* translators: %s: shipping location */
				$errors->add( 'shipping', sprintf( __( 'Unfortunately <strong>we do not ship %s</strong>. Please enter an alternative shipping address.', 'woocommerce' ), WC()->countries->shipping_to_prefix() . ' ' . WC()->customer->get_shipping_country() ) );
			} else {
				$chosen_shipping_methods = WC()->session->get( 'chosen_shipping_methods' );

				foreach ( WC()->shipping()->get_packages() as $i => $package ) {
					if ( ! isset( $chosen_shipping_methods[ $i ], $package['rates'][ $chosen_shipping_methods[ $i ] ] ) ) {
						$errors->add( 'shipping', __( 'No shipping method has been selected. Please double check your address, or contact us if you need any help.', 'woocommerce' ) );
					}
				}
			}
		}

		if ( WC()->cart->needs_payment() ) {
			$available_gateways = WC()->payment_gateways->get_available_payment_gateways();

			if ( ! isset( $available_gateways[ $data['payment_method'] ] ) ) {
				$errors->add( 'payment', __( 'Invalid payment method.', 'woocommerce' ) );
			} else {
				$available_gateways[ $data['payment_method'] ]->validate_fields();
			}
		}

		do_action( 'woocommerce_after_checkout_validation', $data, $errors );
	}