Okla. Stat. tit. 68 § 1802
Within sixty (60) days after this act shall become effective, each Cooperative shall file with the Oklahoma Tax Commission, on forms prescribed thereby, a statement of its total gross receipts derived from the sale and distribution of electric energy during the period beginning January 1, 1943, and ending on the last day of the calendar month next preceding the time for making such statement and shall pay the tax hereinafter levied thereon; and, on or before the twentieth day of each month thereafter each cooperative shall so file such statement of such gross receipts so derived during the next preceding calendar month and pay the tax hereinafter levied thereon; each such statement shall contain such other and further information as the Oklahoma Tax Commission may require and shall be sworn to and verified by an officer of the cooperative.
Okla. Stat. tit. 68, § 1802