Set at custom tax class for a quote item

Question

I'm developing av B2B shop, where prices/discounts are fetched from an API when adding to basket. This is done by overriding Mage_Sales_Model_Quote_Item::calcRowTotal.

Now, based on a variable returned from the API, a quote item price may or may not include tax (25%).

Is there any way to apply a tax on a quote item when adding to basket, even when the product itself does not have a tax class in Magento?

I hope this was properly explained. Many thanks!

Answer 1

use observer sales_quote_collect_totals_before and in the observers function try to set the tax to the product depending on the condtions using setTaxClassId to the product object

public function newTax($observer){
    $quote = $observer->getQuote();
    foreach ($quote->getAllItems() as $quoteItem)
    {
        $product = $quoteItem->getProduct();
        // here you can assign tax to the product depending on your conditions
    }