2026 Oklahoma State Tax Deadlines

Oklahoma business tax deadlines for 2026

C Corporations' deadlines and requirements

C Corporations in Oklahoma must file and pay Corporate Income Tax by April 15, 2027, following the federal due date schedule.

Filing requirements include:

1. Complete Form 512 (Oklahoma Corporate Income Tax Return)
2. File via Oklahoma Taxpayer Access Point
3. Payment must be made by April 15, 2027
4. Mail submissions must be postmarked by the due date

Extension to file taxes in Oklahoma for 2026

The Extension Deadline for Oklahoma corporate income tax returns is October 15, 2027. Form 512ES is required for extensions; payment is still due April 15, 2027.

Pass-through entities

Oklahoma S Corporations and Partnerships tax deadlines for 2026

S Corporations and Partnerships must file in Oklahoma by April 15, 2027.

Required forms include:

1. Form 512S—S Corporation Return
2. Form 512P—Partnership Return

Extension to file S Corporations and Partnerships taxes in Oklahoma for 2026

The Extension Deadline for Oklahoma S Corporations and Partnerships returns is October 15, 2027. Extension forms may be required; payment is still due on the original filing dates.

Oklahoma Individual tax considerations for 2026

Filing requirements and income thresholds

Oklahoma Individuals must file a State income tax return if their gross income exceeds specific thresholds based on filing status.

The flat tax rate for 2026 is:

• 4.75% on all Oklahoma taxable income

Estimated tax deadline for Oklahoma 2026

Estimated tax payments are due on the following schedule for calendar year filers:

• April 15, 2026
• June 15, 2026
• September 15, 2026
• January 15, 2027

Who must make estimated payments

You must make Oklahoma estimated income tax payments during 2026 if you expect to owe a significant amount in Oklahoma income tax after subtracting withholding and credits. Electronic payments are encouraged through the Oklahoma online tax system.

Individual tax deadline for Oklahoma 2026

Individual income tax returns are due April 15, 2027.

Available forms include:

• Form 511—Oklahoma Individual Income Tax Return

Extension to file taxes in Oklahoma for 2026

The Extension Deadline is October 15, 2027, to file your Oklahoma Individual Income tax return. Oklahoma grants a six-month extension without requiring separate extension forms. This is an extension to FILE, not an extension to PAY—payment is still due April 15, 2027.

What Oklahoma tax professionals need to know

Several key considerations make Oklahoma's tax landscape unique for 2026. Oklahoma's flat income tax system provides simplicity and competitive rates. The state's energy-driven economy creates specific tax considerations, and Oklahoma offers various business incentives and earned income credits.

Electronic filing requirements

Oklahoma has implemented electronic filing systems for taxpayers:

• C Corporations and pass-through entities should file electronically through the Oklahoma Taxpayer Access Point
• Individuals can use Oklahoma's online system for free electronic filing
• Business deductions can be processed more efficiently through electronic systems
• Professional preparers must use approved software vendors

Unique Oklahoma tax features for 2026

Oklahoma offers several distinctive tax features, including:

• 4.75% flat rate on all Oklahoma taxable income
• Earned Income Credit available to qualifying taxpayers
• Federal tax deduction—Oklahoma allows the deduction of federal income taxes paid
• Competitive business environment with various incentive programs

Federal Tax Deduction

Oklahoma's federal tax deduction creates specific planning considerations:

• Federal income taxes paid can be deducted on Oklahoma returns
• Creates interaction between federal and state tax planning
• May affect the timing of federal tax payments
• Important for moderate and high-income taxpayers

Earned Income Credit

Oklahoma offers a state Earned Income Tax Credit:

• Based on the federal EITC
• Provides additional tax relief for working families
• Available to qualifying low and moderate-income taxpayers
• Supplements federal EITC benefits

Energy Industry Focus

Oklahoma's significant energy production creates unique tax considerations:

Oil and Gas Industry

• Oil and gas severance taxes
• Working interest depletion allowances
• Enhanced recovery incentives
• Gross production tax on oil and gas
• Special provisions for energy companies

Renewable Energy

• Wind energy tax incentives
• Solar energy development credits
• Renewable energy equipment exemptions
• Alternative energy research credits

Business incentives and credits

Oklahoma provides various business tax incentives:

• Oklahoma Quality Jobs Program
• Investment/New Jobs Tax Credit
• Small Employer Quality Jobs Incentive Act
• Research and Development Tax Credit
• Historic Preservation Tax Credit

Agriculture and Rural Development

Oklahoma's agricultural economy includes special provisions:

• Agricultural equipment sales tax exemptions
• Beginning farmer programs
• Agricultural land use assessment programs
• Rural development incentives
• Drought and disaster relief provisions

Manufacturing and Industrial Development

Oklahoma emphasizes manufacturing development:

• Manufacturing equipment sales tax exemptions
• Industrial development programs
• Aerospace industry incentives
• Job creation tax credits

Native American Considerations

Oklahoma has a significant Native American population and tribal considerations:

• Tribal tax exemptions and sovereignty issues
• Federal Indian employment credits
• Gaming tax provisions
• Coordination between state and tribal tax systems

Transportation and Aerospace

Oklahoma's transportation and aerospace industries have special considerations:

• Aerospace manufacturing incentives
• Transportation equipment exemptions
• Aviation industry tax provisions
• Military contractor benefits

Technology and Innovation

Oklahoma supports technology development:

• Research and development tax credits
• High-tech startup incentives
• University research partnerships
• Innovation and entrepreneurship programs

Retirement income considerations

Oklahoma provides certain retirement income benefits:

• Military retirement pay may be exempt from Oklahoma state income tax
• Social Security benefits are generally exempt from the Oklahoma state income tax
• Pension income considerations for residents
• Senior citizen tax benefits

Professional tax guidance

For complex Oklahoma tax situations, consulting with qualified tax professionals through an accounting firm directory can help ensure compliance and identify available tax-saving opportunities.

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