Procedures for calculation of payment due dates.

(1) Each local governmental entity shall establish procedures whereby each payment request or invoice received by the local governmental entity is marked as received on the date on which it is delivered to an agent or employee of the local governmental entity or of a facility or office of the local governmental entity.

(2) The payment due date for a local governmental entity for the purchase of goods or services other than construction services is 45 days after the date specified in s. 218.73. The payment due date for the purchase of construction services is specified in s. 218.735.

(3) If the terms under which a purchase is made allow for partial deliveries and a payment request or proper invoice is submitted for a partial delivery, the time for payment for the partial delivery must be calculated from the time of the partial delivery and the submission of the payment request or invoice in the same manner as provided in s. 218.73 or s. 218.735.

(4) All payments, other than payments for construction services, due from a local governmental entity and not made within the time specified by this section bear interest from 30 days after the due date at the rate of 1 percent per month on the unpaid balance. The vendor must invoice the local governmental entity for any interest accrued in order to receive the interest payment. Any overdue period of less than 1 month is considered as 1 month in computing interest. Unpaid interest is compounded monthly. For the purposes of this section, the term “1 month” means a period beginning on any day of one month and ending on the same day of the following month.