I'm trying to track down an undefined index error on 'tax_rate' in functions_taxes.php in function zen_get_tax_rate_from_desc on line 274. The input to this function is "Sales Tax" (TEXT_UNKNOWN_TAX_RATE). It appears that $class_id may be incorrect in function zen_get_tax_description($class_id, $country_id = -1, $zone_id = -1) which retrieves the tax description for function zen_get_tax_rate_from_desc. The product non-taxable. country_id and zone_id are correct and match the tax class country and zone. I do not get the error in an unmodified zc v157c.

Can someone please summarize the processing path associated with tax rate determination for both non-taxable and taxable products at checkout for zc 157c?

Thank you!