An extension of time to file your income tax return shall not be granted unless 90% of the tax liability is paid on or before the original due date of the return.
Since the Oklahoma return cannot be completed until the Federal return is completed, the Oklahoma Tax Commission has administratively adopted the policy of honoring the automatic Federal extension, when no additional state tax is due, as an extension of time to file the Oklahoma return. When you file your Oklahoma return, simply enclose a copy of the Federal extension.
You only need to use this form to apply for additional time to file your income tax return when you owe additional Oklahoma income tax or do not have a Federal extension. Also, corporations, partnerships, estates and trusts need to use this form when filing for additional time beyond that granted by the Federal extension. When you file your Oklahoma return, enclose a copy of the Oklahoma Extension.
Remember, you cannot get an extension of time to pay your income tax, but only to file your return. Delinquent penalty of 5% may be charged, if at least 90% of your total tax liability has not been paid by the original due date. Delinquent interest, at the rate of 1.25% per month, may be charged if 100% of your tax liability is not paid by the original due date of the return.
Form 504 Instructions