Add New Custom Field in Woo Commerce Checkout Fields

NewCustomField.php

<?php

// Add New Custom Field
add_action( 'woocommerce_before_order_notes', 'wtwh_add_custom_checkout_field' );  
function wtwh_add_custom_checkout_field( $checkout ) { 
   $current_user = wp_get_current_user();
   $saved_car_no = $current_user->car_no;
   woocommerce_form_field( 'car_no', array(        
      'type' => 'text',        
      'class' => array( 'form-row-wide' ),        
      'label' => 'Car Model Number',        
      'placeholder' => 'ABC123',        
      'required' => false,        
      'default' => $saved_car_no,        
   ), $checkout->get_value( 'car_no' ) ); 
}

// Validation Field
add_action( 'woocommerce_checkout_process', 'wtwh_validate_new_checkout_field' );
function wtwh_validate_new_checkout_field() {    
   if ( ! $_POST['car_no'] ) {
      wc_add_notice( 'Please enter your Car Model Number', 'error' );
   }
}

// Save and Show New Field in WooCommerce Thank You Page, Order Page & Emails
add_action( 'woocommerce_checkout_update_order_meta', 'wtwh_save_new_checkout_field' );
function wtwh_save_new_checkout_field( $order_id ) { 
    if ( $_POST['car_no'] ) update_post_meta( $order_id, '_car_no', esc_attr( $_POST['car_no'] ) );
}
 
add_action( 'woocommerce_thankyou', 'wtwh_show_new_checkout_field_thankyou' );
function wtwh_show_new_checkout_field_thankyou( $order_id ) {    
   if ( get_post_meta( $order_id, '_car_no', true ) ) echo '<p><strong>Car Model Number:</strong> ' . get_post_meta( $order_id, '_car_no', true ) . '</p>';
}
  
add_action( 'woocommerce_admin_order_data_after_billing_address', 'wtwh_show_new_checkout_field_order' );
function wtwh_show_new_checkout_field_order( $order ) {    
   $order_id = $order->get_id();
   if ( get_post_meta( $order_id, '_car_no', true ) ) echo '<p><strong>Car Model Number:</strong> ' . get_post_meta( $order_id, '_car_no', true ) . '</p>';
}
 
add_action( 'woocommerce_email_after_order_table', 'wtwh_show_new_checkout_field_emails', 20, 4 );
function wtwh_show_new_checkout_field_emails( $order, $sent_to_admin, $plain_text, $email ) {
    if ( get_post_meta( $order->get_id(), '_car_no', true ) ) echo '<p><strong>Car Model Number:</strong> ' . get_post_meta( $order->get_id(), '_car_no', true ) . '</p>';
}