Okla. Stat. tit. 62, § 62-310.1

A. Unless otherwise provided by ordinance, officers, boards,

commissions and designated employees of cities and towns,

hereinafter referred to as the purchasing officer, having authority

to purchase or contract against all budget appropriation accounts as

authorized by law shall submit all purchase orders and contracts

prior to the time the commitment is made, to the officer charged

with keeping the appropriation and expenditure records or clerk, who

shall, if there be an unencumbered balance in the appropriation made

for that purpose, so certify in the following form:

I hereby certify that the amount of this encumbrance has been

entered against the designated appropriation accounts and that this

encumbrance is within the authorized available balance of said

appropriation.

Dated this ______ day of _____________, 20____.

___________________________________________

Oklahoma Statutes - Title 62. Public Finance Page 375

Encumbering Officer or Clerk of ___________.

Provided, in instances where it is impossible to ascertain the exact

amount of expenditures to be made at the time of recording the

encumbrance, an estimated amount may be used and the encumbrance

made in like manner as set forth above. Provided, no purchase order

or contract shall be valid unless signed and approved by the

purchasing officer and certified as above set forth by the officer

or clerk charged with keeping the appropriation and expenditure

records. The clerk or encumbering officer shall retain and file one

copy of the purchase order.

B. After satisfactory delivery of the merchandise or completion

of the contract, the supplier shall deliver an invoice. Such

invoice shall state the supplier's name and address and must be

sufficiently itemized to clearly describe each item purchased, its

unit price, where applicable, the number or volume of each item

purchased, its total price, the total of the purchase and the date

of the purchase. The appropriate officer shall attach the itemized

invoice together with delivery tickets, freight tickets or other

supporting information to the original of the purchase order and,

after approving and signing said original copy of the purchase

order, shall submit the invoices, the purchase order and other

supporting data for consideration for payment by the governing

board. All invoices submitted shall be examined by the governing

board to determine their legality. The governing board shall

approve such invoices for payment in the amount the board determines

just and correct.

C. As an alternative to the provisions of subsection B of this

section, the governing body may elect to pay claims and invoices

pursuant to the provisions of subsection A of Section 17-102 of

Title 11 of the Oklahoma Statutes, which provides for the adoption

of an ordinance to ensure adequate internal controls against

unauthorized or illegal payment of invoices. The governing body may

also authorize the chief executive officer or designee to approve

payment of such invoices. In absence of such authority, the

governing board shall approve payment.