Okla. Stat. tit. 11, § 11-36-405

The governing body, by ordinance, shall levy assessments against

the several lots and tracts of land benefited by reason of the

improvement in accordance with its determination and final

adjudication and fix a lien upon the property for the amount of the

assessments. The ordinance shall provide that:

1. The assessments are payable in ten (10) equal annual

installments, with interest thereon at the rate of eight percent

(8%) per annum, payable annually;

2. The installments shall be due and payable on or before the

first day of September of each year following the date of the

passage of the assessing ordinance;

3. The owner of any lot, piece or parcel of land shall have the

right to pay the entire assessment without interest within thirty

(30) days after the date of the publication of the assessing

ordinance;

4. Upon failure to pay an installment the municipal clerk shall

certify the delinquency to the county treasurer to be placed upon

the delinquent tax list of the county for the current year; and 5.

If installments are not paid when due, they shall bear interest at

the rate of twelve percent (12%) per annum, and no earlier than July

1 and no later than July 10 of the following year, shall be

certified to the county treasurer to be placed upon the delinquent

list, and the property shall be sold to pay such delinquent

assessment in the manner provided for the sale of property for

delinquent taxes. Provided, that no such certification shall be

made to the county treasurer unless the city or town clerk shall

have sent a notice of the nature and amount of the assessment by

restricted delivery mail on or before June 1 of said year to the

last-known address of the owner of the assessed property.