'Recalculate Taxes in Woocommerce

I got a Problem. In Woocommerce I added a custom product type (abo), where the user can choose a area size (in square meters) and there is a price per square meter and a dosage information where it says e.g. "You need 0.165kg per squaremeter" (it´s a fertilizer).

So for example if the user chooses 100 square meters and the price per square meter is 2.30€ and the dosage is 0.165kg/sqm the total price of the abo is 37.95€ and at a tax rate of 10.7% the tax amount should be 4.06€.

My Problem now is, I have normal products in the shop as well, where the standard calculation of the price and tax etc. works perfectly fine and you can buy the abo and a normal product.

So my question is, how can I recalculate the tax amount if I got an abo in cart?

I tried a few things for testing so far:

Adding a custom fee (that isn´t what I´m looking for, cause the tax has to be the same on cart, checkout and receipt):

add_action( 'woocommerce_cart_calculate_fees','custom_tax_surcharge_for_swiss', 10, 1 );
function custom_tax_surcharge_for_swiss( $cart ) {
    if(current_user_can('administrator')) :
    
        $percent = 10.7;
    
        // Calculation
        $surcharge = ( $cart->cart_contents_total + $cart->shipping_total ) * $percent / 100;
    
        // Add the fee (tax third argument disabled: false)
        $cart->add_fee( __( 'TAX', 'woocommerce')." ($percent%)", $surcharge, false );
    endif;
}

calc_tax function (I think this one is the one I need) :

/ define the woocommerce_calc_tax callback 
function filter_woocommerce_calc_tax( $taxes, $price, $rates, $price_includes_tax, $suppress_rounding ) { 
    if(current_user_can('administrator')) :
    foreach(WC()->cart->cart_contents as $item) :
        if($item['data']->get_type() == 'abo') :
            $qty = $item['quantity'];
            $ppqm = str_replace(',', '.', get_post_meta($item['product_id'], 'abo_product_price_per_kg')[0]);
            $kgpqm = str_replace(',', '.', get_post_meta($item['product_id'], 'abo_product_kg_qm')[0]);
            $realQty = floatval($kgpqm) * floatval($qty);
            $priceCustom = $priceCustom + $realQty * floatval($ppqm);
            
        endif;
    endforeach;
        
    return $taxes; 
}; 
                 
// add the filter 
add_filter( 'woocommerce_calc_tax', 'filter_woocommerce_calc_tax', 10, 5 );

With the above function I got the problem, that I don´t have the cart contents directly so it could be, that the order of the items isn´t the same as the Tax order which I get from the function. I would also note, that the woocommerce_calc_tax fires twice. I had for debug reasons an output in the console and if I have 2 items in cart, I got 4 outputs.

Hope my Problem is clear and that anyone could help me with that problem.

Thanks in advance.

Solution 1:^[1]

I would look into the tax class for WooCommerce. You can specific target a item with a different tax rate. Unless I'm missing something this should actually work how you need it to out of the box.