Upgrade From 11.5.10 to 12.1.3 - Tax Classification Codes

Client is upgrading from 11.5.10 to 12.1.3 and I understand that tax groups are upgraded to tax classification codes in R12.  One issue that we're having is importing of intercompany AP invoices. 

When the Create Intercompany AP process inserts the invoice header and lines into the open interface a tax classification code is included on the line.  When importing the invoices the import fails with ZX_TAX_RATE_NOT_EXIST error message.  I believe I've tracked down the cause of this error in the ZX_VALIDATE_AP_PKG...the tax classification code doesn't exist as a lookup value in the ZX_INPUT_CLASSIFICATIONS lookup codes and isn't setup as a tax rate.  I guess I expected the rates to be setup by the upgrade but that's not happening.