Mryntu

I saw there are some post like this but I tried that answer and dit not work.

I am learning how to use magento, and What I wan to try is remove all the tax from the cliente when them have add 3 products to the cart.

I am using an observer event. And the function it run is:

Here is the config.xml

<events>
 <checkout_cart_add_product_complete> <!-- identifier of the event we want to catch -->
 <observers>
 <checkout_cart_add_product_complete_handler> <!-- identifier of the event handler -->
 <type>model</type> <!-- class method call type; valid are model, object and singleton -->
 <class>descuentoiva/observer</class> <!-- observers class alias -->
 <method>addCheckout</method> <!-- observer's method to be called -->
 <args></args> <!-- additional arguments passed to observer -->
 </checkout_cart_add_product_complete_handler>
 </observers>
 </checkout_cart_add_product_complete>
<events>

And this is my actual code for the fuction:

public function addCheckout(Varien_Event_Observer $observer)
 
 $cart = Mage::getModel('checkout/cart')->getQuote(); 
 if (count($cart->getAllItems()) >= 3) 
 $products = $cart->getAllVisibleItems();
 foreach($products as $item) 
 echo $item->getPriceInclTax()."<br>"; 
 if ($item->getTaxAmount() > 0) 
 $item->setTaxPercent(0);
 $item->setTaxAmount(0);
 $item->setBaseTaxAmount(0);
 $item->save(); 
 
 
 $cart->save(); 
 
 #die("patata"); 
 

But when I look the checkout it did not work.

You also have to config your event in config.xml. Learn here

Now, we need to use this event checkout_cart_product_add_after and checkout_cart_product_update_after.

In your config.xml

<global>
 ..
 ..
 <events>
 <checkout_cart_product_add_after>
 <observers>
 <my_module_product_add_after>
 <type>singleton</type>
 <class>modulename/observer</class>
 <method>checkout_cart_product_add_after</method>
 </my_module_product_add_after>
 </observers>
 </checkout_cart_product_add_after>
 </events>
 ..
 ..
</global>

Now function checkout_cart_product_add_after() in model/observer.php

public function checkout_cart_product_add_after(Varien_Event_Observer $observer)
 
 $quote = $observer->getEvent()->getQuote(); 
 if (count($quote->getAllItems()) >= 3) 
 $items = $quote->getAllVisibleItems();
 foreach($items as $item) 
 $item
 ->setTaxAmount(0)
 ->setBaseTaxAmount(0)
 ->save();
 
 
 Mage::log('my log', null, 'my-log.log'); //creates log file if this function is called 
 

This will set tax to 0 for all items that are in cart. You would want to check sales_flat_quote_item table.

Because you would also want to check this event on item update on cart, so you have to set another event for this checkout_cart_product_update_after.

you can call same function for this event too.

I haven't tested, but this should work.