(1)
The Commissioner must,—
in the case of a decision by the Commissioner at the conclusion of a proceeding, notify all the parties to the proceeding in writing:
in the case of the Commissioner’s exercise of any other discretionary power under the Act or the regulations, notify the party or parties affected in writing.
(2)
For the purpose of an appeal under section 170 of the Act, a decision is given—
when the notice of the decision is sent by the Commissioner; or
if a person to whom the notice has been sent requires the Commissioner to notify the reasons for the decision, when the reasons for the decision are sent by the Commissioner.