Set tax on checkout based off user payment selection woocommerce - wordpress

Question

When a user is on my woocommerce store checkout, I want to set the tax to 0 if they choose a certain payment gateway like "paypal_pro", "cheque", "bacs", or in my case "wdc_woo_credits". Which is a woocredits plugin that allows users to pay with credits instead of a credit card.
I know this function sets the taxes correctly because when I print_r($cart_object) I see I set all the taxes to 0, but yet the checkout still applies the tax in the total.
I think I need a function that recalculates the taxes after I set it using the function below.
add_action( 'woocommerce_cart_calculate_fees','shipping_method_discount', 20, 1 );
function shipping_method_discount( $cart_object ) {
if ( is_admin() && ! defined( 'DOING_AJAX' ) ) return;
$chosen_payment_method = WC()->session->get('chosen_payment_method');
//if( $chosen_payment_method == 'cheque' ){
if( $chosen_payment_method == 'wdc_woo_credits' ){
$cart_object->set_cart_contents_taxes(0);
$cart_object->set_cart_contents_tax(0);
$cart_object->set_subtotal_tax(0);
$cart_object->set_shipping_tax(0);
$cart_object->set_total_tax(0);
$cart_object->set_fee_tax(0);
$cart_object->set_fee_taxes(0);
$cart_object->set_subtotal_tax(0);
foreach($cart_object->cart_contents as $product){
$cart_object->cart_contents[$product['key']]['line_tax'] = 0;
$cart_object->cart_contents[$product['key']]['line_subtotal_tax'] = 0;
$cart_object->cart_contents[$product['key']]['line_tax_data']['subtotal'] = 0;
$cart_object->cart_contents[$product['key']]['line_tax_data']['total'] = 0;
}
}
//echo '<pre>'; print_r($cart_object); echo '</pre>';
}
This function detects what payment selection they choose and re-runs the update checkout function. But yet the tax is still in the total.
add_action( 'woocommerce_review_order_before_payment', 'refresh_payment_methods' );
function refresh_payment_methods(){
// jQuery code
?>
<script type="text/javascript">
(function($){
$( 'form.checkout' ).on( 'change', 'input[name^="payment_method"]', function() {
$('body').trigger('update_checkout');
});
})(jQuery);
</script>
<?php
}

Answer 1

After lots of googling, i found out that I don't need to mess with the cart totals at all. I need to alter the current logged in customer.
I can do it with this function which removes tax for the current logged in user.
WC()->customer->set_is_vat_exempt( true );
all this goes in functions.php. You still need the woocommerce_review_order_before_payment function from above which triggers the ajax. So here's the complete code to hide tax on a certain payment gateway for only logged in users.
// calculate fees on checkout page
add_action( 'woocommerce_cart_calculate_fees','shipping_method_discount', 20, 1 );
function shipping_method_discount( $cart_object ) {
if ( is_admin() && ! defined( 'DOING_AJAX' ) ) return;
$chosen_payment_method = WC()->session->get('chosen_payment_method');
//if( $chosen_payment_method == 'cheque' ){
if( $chosen_payment_method == 'wdc_woo_credits' ){
// if user buys with credits, dont allow tax.
WC()->customer->set_is_vat_exempt( true );
}else{
// if user buys with credit card, allow tax
WC()->customer->set_is_vat_exempt( false );
}
}
// refresh the checkout page totals once user selects
add_action( 'woocommerce_review_order_before_payment', 'refresh_payment_methods' );
function refresh_payment_methods(){
// jQuery code
?>
<script type="text/javascript">
(function($){
$( 'form.checkout' ).on( 'change', 'input[name^="payment_method"]', function() {
$('body').trigger('update_checkout');
});
})(jQuery);
</script>
<?php
}