Okla. Stat. tit. 68, § 68-500.20: Precollection and remittance of tax by suppliers

A. The tax imposed by Sections 500.4 and 500.4B of this title,

measured by motor fuel removed by a licensed supplier from a

terminal or refinery in this state other than a bulk transfer, shall

be precollected and remitted on behalf of the retail consumers to

the state by the supplier, as shown in the records of the terminal

operator, who removes the taxable gallons.

B. The supplier, and each reseller, shall list the amount of

tax as a separate line item on all invoices or billings.

C. All tax to be paid by a supplier with respect to gallons

removed on the account of the supplier during a calendar month shall

be due and payable on or before the twentieth day of the following

month unless such day falls upon a weekend or state or banking

holiday in which case the liability would be due the next succeeding

business day.

D. A supplier shall remit any late taxes remitted to the

supplier by an eligible purchaser and shall timely notify the

Commission of any late remittances if that supplier has previously

given notice to the Commission of an uncollectible tax amount

pursuant to subsection B of Section 500.24 of this title. For the

purposes of reporting a payment received on previously claimed

uncollectible taxes, any payments made to a supplier on a debt or

account shall be applied first proportionally to the gallons sold

and the tax thereon, and secondly to interest, service charges, and

any other charges.