in the event of interlocutory revision or where the Board of Appeal deems an appeal to be allowable, if such reimbursement is equitable by reason of a substantial procedural violation, or
if the appeal is withdrawn before the filing of the statement of grounds of appeal and before the period for filing that statement has expired.
The appeal fee shall be reimbursed at 50% if the appeal is withdrawn after expiry of the period under paragraph 1(b), provided withdrawal occurs:
if a date for oral proceedings has been set, at least four weeks before that date;
if no date for oral proceedings has been set, and the Board of Appeal has issued a communication inviting the appellant to file observations, before expiry of the period set by the Board for filing observations;
in all other cases, before the decision is issued.
The department whose decision is impugned shall order the reimbursement if it revises its decision and considers reimbursement equitable by reason of a substantial procedural violation. In all other cases, matters of reimbursement shall be decided by the Board of Appeal.