The standard of review is the degree of deference an appeal court gives to the decision under appeal. At the Federal Court of Appeal in a tax matter, the standard determines whether the Tax Court's decision can be disturbed and is usually the decisive issue.
Questions of law — the interpretation of the Income Tax Act or the legal test to be applied — are reviewed for correctness, with no deference. Questions of fact, and most questions of mixed fact and law, are reviewed only for "palpable and overriding error," a demanding standard that defers to the trial judge who heard the witnesses. An appeal that merely disputes how the evidence was weighed faces the higher hurdle; one that identifies an extricable error of law has a far better prospect.