Can, and Should, the Parol Evidence Rule be Invoked By or Against Tax Authorities in Tax Litigation? Distilling lessons from U.S. jurisprudence

In recent years, Canada’s courts have expressed a number of conflicting views about whether the parol evidence rule can be invoked by or against the Minister of National Revenue (Minister) in tax disputes. Unfortunately, the courts in these cases did not elaborate, to a sufficient extent, on the justifications for their position on this issue. It is an open question, therefore, whether and why the parol evidence rule should (or should not) apply to the Minister. In the U.S., Federal and State courts have explored this same issue extensively, and have produced meaningful jurisprudence that can be a source of influence for Canada as well as for any other jurisdiction whose law on this issue may be similarly unsettled and/or underdeveloped. The purpose of this paper is to distill lessons from the US jurisprudence. These lessons can then be transplanted elsewhere as a source of influence and guidance. For the purpose of example, the paper will apply these lessons to address the issue in the contexts of Canadian law.