Isah – Tax Court of Canada notes obiter that it can address incorrectly computed assessment interest
Imperial Oil indicated that the Tax Court has no jurisdiction to hear an appeal on the computation of refund interest. This is not to be confused with normal assessment interest, as to which Russell J stated:
[I]nterest relief [is] not a matter over which this Court has jurisdiction (unless the wrong interest rate was used or otherwise a wrong calculation of the interest was made, thereby affecting the balance of the appealed (re)assessment).
Neal Armstrong. Summary of Isah v. The Queen, 2018 TCC 28 under s. 171(1).