Any dues owed to the deceased are the property of the heirs that cannot be disposed of without their consent
liabilities other people owe your father are the right of his inheritors after paying off his debts and executing his Shar`y (Islamic legal) will. Therefore, it is invalid to waive the 80 riyals unless otherwise validated by heirs of full age as far as their respective shares are concerned. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.