[FIXED] How to add a percentage based surcharge (plus tax of surcharge) to all transactions

Issue

I'm trying to add a percentage based fee from Woocommerce subtotal in both cart and checkout. However, have this fee made up with a 5% surcharge of subtotal + 20% tax of the 5% surcharge.

• Subtotal: £100
• Surcharge: £6 (<- £5 (5%) + £1 Tax Surchange (20%)

I have managed to add the 5% percentage based fee of Subtotal. However, how do you add the 20% of $surcharge on top?

Also, will this type of change be effective for emails too? (As well as cart / checkout) is

Any advice would be appreciated.

Thanks in advance.

    add_action( 'woocommerce_cart_calculate_fees','custom_adminfee_surcharge' );
    function custom_adminfee_surcharge() {
      global $woocommerce;
        if ( is_admin() && ! defined( 'DOING_AJAX' ) )
            return;
$percentage = 0.05 * .20;
        $surcharge = ( $woocommerce->cart->subtotal + $woocommerce->cart->shipping_total ) * $percentage;   
        $woocommerce->cart->add_fee( 'Surcharge', $surcharge, true, '' );
    }

Solution

This should be 5% of the subtotal then 20% of that 5%...

add_action( 'woocommerce_cart_calculate_fees','custom_adminfee_surcharge' );
function custom_adminfee_surcharge() {
  global $woocommerce;
    if ( is_admin() && ! defined( 'DOING_AJAX' ) ) return;

    $percentage = ( $woocommerce->cart->subtotal + $woocommerce->cart->shipping_total ) * 0.05;
    $surcharge = $percentage * 0.20;
    $total_charges = $percentage + $surcharge;

    $woocommerce->cart->add_fee( 'Surcharge', $total_charges, true, '' );
}

Answered By - Bossman