The Clerk-Treasurer shall disburse funds only as authorized by Council by way of an appropriation. No obligations shall be incurred and no expenditure shall be made unless approved by the Clerk-Treasurer with certification that there is an unencumbered balance of appropriated and available funds. No check for the payment of any claim shall be issued until such claim shall have been approved, in writing, by the head of the department or officer for whom the obligation or claim was incurred, and in the case of purchases, with any further written approval as may be established by Council. The Clerk-Treasurer shall, before making payment of any item, audit all such bills, invoices, payrolls, or other claims against the Municipality and shall determine the regularity and correctness of such items.