Okla. Stat. tit. 36, § 2685

Every corporation doing business pursuant to this Article is hereby declared to be a nonprofit, charitable and benevolent institution and to be exempt from state, county, district, municipal and school taxes, including the taxes prescribed by the Oklahoma Insurance Code, excepting only the fees prescribed by Section 321 of Title 36, Oklahoma Statutes, and taxes on real and tangible personal property situated within this state. Laws 1973, c. 104, § 15, emerg. eff. May 3, 1973.