Whenever prior to the confirmation of the reassessment any principal payments have been made on any assessment or on any bond issue to represent any such assessment, the owner of record of the property against which such assessment was levied, at the time such payment was made, or where a purchaser under a contract of purchase or a lessee under a lease, pursuant to the terms of which contract of purchase or lease, is required to and has made such payments upon the original assessment or bonds, then such purchaser or lessee shall be entitled to receive a refund of an amount of the difference between the original assessment and the reassessment in the proportion that such payments made by him bears to the original assessment, with respect to the lot or parcel of land for which such payments were made. The balance of any such appropriation, as determined by the reassessment, shall be credited pro rata to the bonds in payment thereof, applying such payment first to the interest due and then upon the principal. Thereafter the treasurer shall pay to the holder of each bond the payment so credited from the bond and assessment redemption fund. The treasurer is hereby authorized and directed to make all payments of refunds as authorized by this chapter.