Upon the receipt of any payment under this act, it shall be the duty of the collector of taxes to credit the amount thereof on the tax duplicates in his office against the delinquent taxes, penalties, interest, and costs due by such officer or employe, crediting payments from time to time against the taxes for the earliest years still due and owing, and he shall transmit to such officer or employe a receipt for the amount of the delinquent taxes, penalties, interest, and costs so paid by deduction from his salary or compensation.
72 P.S. § 5688