Determine if Tax Codes are Manually Created or System Generated.

Manually created tax codes are assigned with positive Internal IDs. System generated tax codes and tax groups imported through Setup > Accounting > Use State Sales Tax Tables are assigned with negative Internal IDs.

To display Internal Ids, perform the following:

1. Navigate to Home > Set Preferences.
2. On General tab and Defaults portlet, mark Show Internal Ids.
3. Click Save.