Okla. Stat. tit. 68 § 208
Any notice required by this article, or any state tax law, to be given by the Tax Commission shall be in writing and may be served personally or by mail. If mailed, it shall be addressed to the person to be notified at the last-known address of such person. As used in this article or any other state tax law, "last-known address" shall mean the last address given for such person as it appears on the records of the division of the Tax Commission giving such notice, or if no address appears on the records of that division, the last address given as appears on the records of any other division of the Tax Commission. If no such address appears, the notice shall be mailed to such address as may reasonably be obtainable. If the Tax Commission receives an address from the United States Postal Service as a result of a change of address submitted to the United States Postal Service, "last-known address" shall mean the address provided to the United States Postal Service. The mailing of such notice shall be presumptive evidence of receipt of the same by the person to whom addressed. If the notice has been mailed as provided in this section, failure of the person to receive such notice shall neither invalidate nor be grounds for invalidating any action taken pursuant thereto, nor shall such failure relieve any taxpayer from any tax or addition to tax or any interest or penalties thereon.
Okla. Stat. tit. 68, § 208