The comptroller shall deduct from the amount of any credit or warrant all amounts which the payee may owe the city, and where there has been an assignment thereof he shall likewise deduct as well all amounts which the assignee may owe the city. Should the amounts owing exceed the amount of the warrant, the amounts thus deducted shall be credited pro tanto on the obligations owing the city. An assignment of the claim shall not defeat the right of the city to deduct the amount of the debt from the amount due the claimant. The claimant or his assignee may appeal from the action of the comptroller in so deducting any amount from the claim in the manner provided for appeals in section 14-813. The city treasurer may likewise deduct from the amount of any warrant city taxes and special assessments which have not been deducted by the comptroller.