Product tax calculation in magento

Magento handles product tax calculation on its own. But there are times when we need manual tax calculation for our products.

$_item->getTaxAmount() gives us the tax amount applied on the product. But there is yet another way to calculate tax.
Click here to list all taxes in magento 2

Load your product

$productId = 10; // for example
$_product = Mage::getModel('catalog/product')->load($productId);

Next we will calculate the tax rate percent. But for that we will require customer address, store information and product tax class id.

// product tax class id
$tax_class_id = $_product->getTaxClassId(); 
//store
$store = Mage::app()->getStore(); //store
// address
$customerAddressId = Mage::getSingleton('customer/session')->getCustomer()->getDefaultShipping();
if ($customerAddressId){
    $address = Mage::getModel('customer/address')->load($customerAddressId);
}

Get product tax percent

$taxCalculation = Mage::getModel('tax/calculation');
$request = $taxCalculation->getRateRequest($address, null, null, $store);
$percent = $taxCalculation->getStoreRate($request->setProductClassId($tax_class_id), $store);

Calculate product tax amount

// get product price including tax
$price = Mage::helper('tax')->getPrice($_product, $_product->getFinalPrice());

$tax_amount = round($price/(100+$percent)*$percent,2);

$tax_amount has been rounded upto 2 decimal places.

Happy coding 🙂