There are two methods for handling Canadian and US Tax together:

1) Use the State.County.City tax structure and define the Canadian province as a state of US, using the location based tax logic.or

2) Define VAT Tax codes for the Canadian rates and put the correct tax code on the customer, so it will default to the invoice during entry.
 

Lockbox Interface : Load Overpayment/Remaining Amount as On-Account

Navigate to Setup->Receipt->AutoCash Rule Sets and select the one you are using. Change the default value of Unapplied to On  Account for Remaining Amount field.

Autocash Rule sets are attached at System Options and at the Customer profile Class level. If there is no rule attached to
the profile Class level, the rule at the system option would be used as a default Rule.

Have a Oracle Question
Do you have an Oracle Question?

Oracle Books
Oracle Certification, Database Administration, SQL, Application, Programming Reference Books

Oracle Application
Oracle Application Hints and Tips

Oracle Home
Oracle Database, SQL, Application, Programming Tips