Where -

(a) in respect of any period a designated person or deciding officer has granted supplementary welfare allowance to or in respect of a person who, though entitled to any other benefit, pension, assistance, allowance or supplement under this Act (in this section referred to as "relevant payment"), is not in receipt of a relevant payment, and

(b) the supplementary welfare allowance is in excess of the amount which would have been granted to that person if he or she had been in receipt of a relevant payment, and

(c) the designated person or deciding officer has certified to the Minister the amount (in this section referred to as "the excess") so paid in excess in respect of that period,

the Minister may reduce any such relevant payment which is or may become payable to the person during the relevant continuous period of entitlement to that relevant payment by the amount of the excess and the amount shall be treated as having been paid on account of the relevant payment.