$product = Bitrix\Catalog\Model\Product::getList(array(
"filter" => array("ID" => $arItem["ID"])
))->Fetch();
if ($product["VAT_ID"]) {
$arVat = Bitrix\Catalog\VatTable::getById($product["VAT_ID"])->Fetch();
echo '<pre>';
print_r($arVat);
echo '</pre>';
exit;
}