“(1) In the case of a contribution paid by or in respect of a person after the due date, where: (a) the contribution is paid after the time when it would, under regulation 4 or 5 above, have been treated as paid for the purposes of entitlement to contributory benefit; and (b) it is shown to the satisfaction of an officer of the Inland Revenue that the failure to pay the contribution before that time is attributable to ignorance or error on the part of that person or the person making the payment and that that ignorance or error was not due to any failure on the part of such person to exercise due care and diligence an officer of the Inland Revenue may direct that, for the purposes of those regulations, the contribution shall be treated as paid on such earlier day as the officer considers appropriate in the circumstances, and those regulations shall have effect subject to any such direction.”