Okla. Stat. tit. 68, § 68-500.43: Payment of tax by consumer

In the event the tax imposed by this act is not precollected and

must be collected from the consumer in accordance with Section 28 of

this act, the tax is due and payable by the consumer on the first

day of each month for the preceding calendar month, and if not paid

on or before the 15th day of the following month, shall be

delinquent. The consumer shall file with the Commission, on forms

furnished by the Commission, a return verified by affidavit showing

in detail the total purchase price of the motor fuel, the number of

gallons purchased, the price per gallon, the location of the

purchase and any other information the Commission may deem

reasonably necessary. With each return, the consumer shall remit to

the Commission the amount of tax shown on the return to be due.

Reports timely mailed shall be considered timely filed. If a report

is not timely filed, interest shall be charged from the date the

report should have been filed until the report is actually filed.