I'm adding one extra attribute (customer group id as drop down field) in billing information at checkout .So based on this selection order review section should calculate tax.

Basically i'm using extension to add extra attributes in billing section.it will effect after order placed(we know all information saved in quote model temp.once order placed click it will store all information in db permanently)

In later time its calculating properly because customer information available in db. So i enable path hints to find out file.but i'm not getting exact file contains logic of tax calculation based on customer group id.I hope i give proper information.thanks in advance.

1 Answer 1


There's actually an entire Tax module, under app/code/core/Mage/Tax. The tax Helper and Tax Calculation model sound like what you're looking for.

Here's one of my favorite sites to sort through Magento classes/functions: http://freegento.com/doc/annotated.html

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