Okla. Stat. tit. 62, § 62-305.1: Municipal or public utility billing - Payment without

verification - Late charges - Discounts.

The governing board of a municipality shall be authorized to

allow and pay the regular periodic billings of any municipal utility

or of any public utility whose rates are fixed by, and are subject

to the approval of, the Oklahoma Corporation Commission or any other

public regulatory body or board of any utility cooperative for

services furnished by the utility to the municipality without the

issuance of a purchase order and filing of an invoice by such

municipal or public utility, provided, further, that no municipal or

public utility shall attach a late charge or deny a discount on any

bill until a thirty-day period has lapsed from the receipt of the

bill.