We are doing business with a canada company and they are a coporation, DO they need to complete a W-8BEN or W-ECI. Also, is there any other certification that they should sending in with the W-8 to claim treaty and advoid 30% backup withholding?

Off-hand, since they are a corporation, I doubt that any type of Form W-8 is required.

To know for sure would require some research with the U.S.-Canada Tax Treaty, and I cannot such research without being compensated.