Okla. Stat. tit. 18, § 437.25

Each cooperative and each foreign corporation transacting business in this state pursuant to this act shall pay annually, on or before the thirty-first day of August, to the Oklahoma Tax Commission, a fee of One Dollar ($1.00) for each one hundred persons or fraction thereof to whom electricity is supplied within the state by it, as of June thirtieth preceding, but shall be exempt from all other excise and income taxes whatsoever. Laws 1939, p. 270, § 26.