The registrant used one methodology for computing its input tax credit claims in its 1998 and 1999 GST returns for those years, then in its 2000 GST return claimed additional input tax credits in respect of costs incurred in 1999 and 1998 based on a revised methodology (which was also acknowledged by the Minister to be fair and reasonable).
In finding that the additional ITC claims of the registrant were permitted, and rejecting the Minister's submission that selecting one methodology should preclude the registrant from later switching to another methodology in respect of the same taxation year, Stratas J.A. stated (at para. 42):
When an election is to be made and when it is irrevocable, Parliament's practice is to use express words in the GST provisions of the Act. There are no express words of irrevocable election concerning the taxpayer's choice of method.
Moreover, s. 225(3) contemplated "that more than one claim for a taxation year may be made at different times as long as the same amount is not claimed twice" (para. 33).