Okla. Stat. tit. 68, § 68-216: Extension of time for filing return

The Tax Commission, whenever in its judgment good cause exists

and pursuant to written request, may grant a reasonable extension

for the filing of any return required under any state tax law. The

Tax Commission shall keep a record of every extension granted with

the reason therefor. Except in the case of corporation income or

franchise tax returns, if franchise tax returns are filed at the

same time as the corporate income tax return, the time for filing

any return may not extend in the aggregate later than one-half (1/2)

the period of time for which any such return is filed under the

particular state tax law involved nor may any such extension extend

the date on which any payment of a state tax is due. An extension

not to exceed seven (7) months for the filing of corporation income

or franchise tax returns, if franchise tax returns are filed at the

same time as the corporate income tax return, shall be allowed. Any

extension granted for the corporate income tax return shall be

deemed to cover the filing of a franchise tax return if a taxpayer

elects to file the franchise tax return at the same time as the

corporate income tax return. An extension shall not extend the date

for payment of the state income or franchise tax due. In case an

extension is granted, the taxpayer may file a tentative return on or

before the date when the return is required by any state tax law

showing the estimated amount of tax for the period covered by the

return and may pay the estimated tax or the first installment

thereof at the time of filing such tentative return and no interest

or penalty shall attach or be payable on sums so paid in due course.