In the course of finding that the taxpayer was estopped from raising the issue of residency after the Federal Court of Appeal had already ruled on the matter (see summary under res judicata), Rip CJ also noted that an assessment of interest on federal taxes did not, in itself, confer a right to appeal those taxes. He stated (at para. 19):
Subsection 152(1) of the Act provides for the Minister to assess tax for the year as well as interest and penalties. An assessment of interest is distinct from an assessment of tax, it is the result of a tax assessment.