Amount withdrawn but not repaid may be deemed as income— In case of default of repayment of instalments due under sub-rule (2) or sub-rule (3) or sub-rule (4) of rule 71 or where the amount withdrawn is not utilised for the purpose for which it is withdrawn, the [Chief Commissioner or Commissioner] may at his discretion order that the amount of the withdrawal or the amount outstanding shall be added to the total income of the employee for the year in which the default occurs or the withdrawn amount is finally held not to have been utilised for the purpose for which it is withdrawn, and the [Assessing Officer] shall assess the employee accordingly