Okla. Stat. tit. 68, § 68-208: Notice of hearing

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.