under sections 69 to 71 and under sections 73 and 74 providing for the making and recovery of charges in respect of any services, may provide for the reduction of the sums which would otherwise be payable by a Health Board to the persons by whom those services are provided by the amount of the charges authorised by the regulations in respect of those services;

for the purposes of section 70(1) in relation to appliances provided as part of the general dental services or the general ophthalmic services under Part II, may provide for the reduction of the sums which would otherwise be payable by a Health Board to the persons by whom those services are provided by the amount of the charges authorised by section 70(1) in respect of those appliances.