any notice or other document is required to be given or sent to the clerk to the appeal tribunal or to an officer authorised by the Secretary of State, that notice or document shall be treated as having been so given or sent on the day that it is received by the clerk to the appeal tribunal or by an officer authorised by the Secretary of State, as the case may be, and

any notice (including notification of a decision of the Secretary of State) or other document is required to be given or sent to any person other than the clerk to the appeal tribunal or to an officer authorised by the Secretary of State, as the case may be, that notice or document shall, if sent by post to that person’s last known address, be treated as having been given or sent on the day that it was posted.