There is an OSS note 441456, but it is not available anymore (internal use/reworking). It would be nice to see what it has as I remember it tells you what you need to do to add certain information for SD/FI.
Other than the above:-
- http://sap.ittoolbox.com/groups/technical-functional/sap-acct/canadian-sales-tax-on-us-sales-to-canada-635421
- http://scn.sap.com/thread/3216776
Regards
Waza