The Supreme Court of Canada has weighted in on how the Canada Interest Act should be applied. This article from the Lawyers Weekly summarizes the case:
http://www.lawyersweekly-digital.com/lawyersweekly/3551/MobilePagedReplica.action?pg=2#pg2
http://www.lawyersweekly-digital.com/lawyersweekly/3551/MobilePagedReplica.action?pg=4#pg4