title: Set a Zero tax rate on a cart fee in WooCommerce
body: <p>In woocommerce I am adding progressive fee based on product categories with the code below <em>(from this <a href="https://stackoverflow.com/questions/51274523/progressive-cart-item-fee-based-on-state-and-on-product-category-in-woocommerce">answer thread</a>)</em> and it works well:</p>
  
  <pre><code>add_action( 'woocommerce_cart_calculate_fees', 'wc_custom_surcharge', 20, 1 );
  function wc_custom_surcharge( $cart ) {
      if ( is_admin() &amp;&amp; ! defined( 'DOING_AJAX' ) )
          return; // Exit
  
      ## Your Settings (below) ##
  
      $categories      = array(19);
      $targeted_states = array('FL');
      $base_rate       = 1;
  
      $user_state = WC()-&gt;customer-&gt;get_shipping_state();
      $user_state = empty($user_state) ? WC()-&gt;customer-&gt;get_billing_state() : $user_state;
      $surcharge  = 0; // Initializing
  
      // If user is not from florida we exit
      if ( ! in_array( $user_state, $targeted_states ) )
          return; // Exit
  
      // Loop through cart items
      foreach ( $cart-&gt;get_cart() as $cart_item ) {
          if ( has_term( $categories, 'product_cat', $cart_item['product_id'] )  ){
              // calculating fee based on the defined rate and on item quatinty
              $surcharge += $cart_item['quantity'] * $base_rate;
          }
      }
  
      // Applying the surcharge
      if ( $surcharge &gt; 0 ) {
          $cart-&gt;add_fee( __("State Tire Fee", "woocommerce" ), $surcharge, FALSE, '' );
  }
  </code></pre>
  
  <blockquote>
    <p>My problem is that I want to set this fee <strong>as NOT taxable</strong>.</p>
  </blockquote>
  
  <p>I have tried severals codes and things but just don't get it. </p>
  
  <p>Any help or track will be really appreciated.</p>