Oklahoma State Tax Guide
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Oklahoma State Tax Guide
Oklahoma Key deadlines (tax year 2025, return filed in 2026)
- Filing deadline: Apr 15, 2026
- Extension request deadline: Apr 15, 2026
- Extended return deadline: Oct 15, 2026 (6-month extension)
- Payment deadline: Apr 15, 2026
- Differs from federal: No
To avoid late-payment penalties, you must pay at least 90% of your total Oklahoma tax liability by the original April deadline. How to Make Extension Payments • Online (OkTAP): Pay by credit card, EFT, or e-check. All payment types accepted through the Oklahoma Taxpayer Access Point. • Mail: Use Form 504-I and mail to: Oklahoma Tax Commission, P.O. Box 26890, Oklahoma City, OK 73126-0890.
If the due date for filing your return falls on a. Saturday, Sunday, or legal holiday, your return is due by the next regular working day.
October 15, 2026 (6-month extension)
Relevant Links
Payment rules
To avoid late-payment penalties, you must pay at least 90% of your total Oklahoma tax liability by the original April deadline. How to Make Extension Payments • Online (OkTAP): Pay by credit card, EFT, or e-check. All payment types accepted through the Oklahoma Taxpayer Access Point. • Mail: Use Form 504-I and mail to: Oklahoma Tax Commission, P.O. Box 26890, Oklahoma City, OK 73126-0890.
Payment options
Payment plan availability
Available: Yes
If you cannot afford to pay your full tax liability by the deadline, the Oklahoma Tax Commission (OTC) allows you to set up a monthly payment plan. Once your official billing notice arrives, log into your OkTAP, locate the payment options panel, and select "Request a Payment Plan."
Filing forms
Regular filing
- Federal form 4868
Extension
- Form 504-I - Oklahoma Application for Extension of Time to File an Individual Income Tax Return · Download form
Oklahoma Refund Tracking
Do I need to file?
If you have an approved federal tax extension and do not expect to owe any Oklahoma income tax, Oklahoma automatically grants you an additional six months to file your state return. In this situation, you are not required to submit a separate Oklahoma extension request, and your state filing deadline is extended from April 15, 2026 to October 15, 2026. However, if you anticipate owing Oklahoma state income tax, you must take additional steps. Taxpayers with a balance due are required to file Form 504-I, the Oklahoma Application for Extension of Time to File an Individual Income Tax Return, and pay the estimated tax owed by April 15, 2026 to avoid penalties and interest. When you eventually file your Oklahoma return, you should also include documentation of your approved federal extension.
Filing methods
Online filing
Federal form 4868
Mail filing
Form 504-I mail to: Oklahoma Tax Commission, P.O. Box 26890, Oklahoma City, OK 73126-0890.
