2027 Oklahoma Tax Deadlines

Last updated: August 5, 2026

Key Oklahoma tax dates at a glance

• April 15, 2027: First Individual estimated payment.
• June 15, 2027: Second Individual estimated payment.
• September 15, 2027: Third Individual estimated payment.
• January 18, 2028: Fourth Individual estimated payment.
• March 15, 2028: Calendar-year S Corporation and Partnership returns and payments.
• April 18, 2028: Calendar-year C Corporation return, paper-filed Individual return, and related payments.
• April 20, 2028: Calendar-year electronically filed Individual return if payment is also made electronically by that date.
• September 15, 2028: Extended S Corporation and Partnership returns, file only.
• October 16, 2028: Extended C Corporation and Individual returns, file only.

When are Oklahoma taxes due in 2027?

Oklahoma 2027 calendar-year C Corporation and Individual returns are generally due April 18, 2028, while S Corporation and Partnership returns are due March 15, 2028. Estimated payments, extensions, franchise tax, and gross production tax should be tracked separately.

When is the Oklahoma C Corporation return due?

Oklahoma C Corporations should plan around April 18, 2028, for the calendar-year corporate-facing return, tax, or business-level filing noted on this page.

• Form 512: Corporation Income Tax Return.
• Form OW-8-ESC: Corporate, fiduciary, and partnership estimated tax coupon.
• Form 504: Oklahoma extension form when a valid federal extension does not apply, or Oklahoma tax is due.
• Form 200-F: Franchise Tax Return when filed separately.
• File and pay through OkTAP.

What are Oklahoma C Corporation extension rules?

The extended filing deadline for the main calendar-year Oklahoma corporate-facing return is October 16, 2028. The extension is to file only, and tax or required payments remain due by April 18, 2028.

When are Oklahoma S Corporation and Partnership returns due?

Oklahoma S Corporations should plan around March 15, 2028, and Partnerships should plan around March 15, 2028.

Which Oklahoma pass-through forms are required?

Use the applicable Oklahoma pass-through return and related payment or owner-reporting forms for the entity type and election facts.

• Form 512-S: Small Business Corporation Income and Franchise Tax Return.
• Form 504: Oklahoma extension form when a valid federal extension does not apply, or Oklahoma tax is due.
• Form 514: Partnership Income Tax Return.

What are Oklahoma pass-through extension rules?

The extended filing deadline for calendar-year Oklahoma S Corporation and Partnership returns is September 15, 2028. The extension is to file only, so tax, withholding, composite, or entity-level payments should be handled by the original deadline.

When is the Oklahoma Individual income tax return due?

Calendar-year Oklahoma Individual income tax returns and payments are due April 18, 2028, or April 20, 2028, when the e-file and electronic-payment rule applies.

• Form 511: Resident Individual Income Tax Return.
• Form 511-NR: Nonresident and Part-Year Resident Income Tax Return.
• Form OW-8-ES: Estimated Tax Coupon.
• Form 504: Oklahoma extension form when a valid federal extension does not apply, or Oklahoma tax is due.

What Oklahoma Individual rate and residency issues should be checked?

Tax year 2027 Individual instructions should be checked for final rate tables, standard deductions or exemptions, residency rules, retirement-income treatment, credits, estimated-payment thresholds, and any filing-year changes specific to Oklahoma.

When are Oklahoma estimated payments due?

Oklahoma estimated-payment planning should be coordinated with withholding, owner payments, franchise tax, and gross production or industry-specific taxes.

• April 15, 2027: First estimated payment.
• June 15, 2027: Second estimated payment.
• September 15, 2027: Third estimated payment.
• January 18, 2028: Fourth estimated payment.

Who must make Oklahoma estimated payments?

Taxpayers should use the final 2027 Oklahoma instructions to confirm estimated-payment thresholds, safe-harbor rules, credits, withholding, pass-through owner treatment, and electronic-payment requirements.

What are Oklahoma extension deadlines?

Oklahoma extension deadlines are September 15, 2028, for pass-through filings, October 16, 2028, for corporate-facing filings, and October 16, 2028, for Individual returns. Extensions add filing time only; payment deadlines remain tied to the original return due dates.

What Oklahoma-specific rules should tax professionals watch for 2027?

Beyond the core return deadlines, Oklahoma tax professionals should track state-specific rate, credit, local-tax, industry, and filing-method rules before the 2027 season locks.

• Oklahoma uses a three-bracket graduated Individual income tax structure with a 4.5% top rate for 2027.
• Individual electronic filing through OkTAP can use the April 20 timing only when the return is e-filed, and payment is made electronically by the required date.
• Franchise tax, pass-through withholding, and owner reporting should be reviewed separately from the annual income-tax return.
• Oklahoma's Earned Income Credit, Social Security subtraction, and military retirement pay exemption should be reviewed with the current Form 511 instructions.
• Gross production and severance-tax items can matter for oil, gas, energy, and mineral clients.
• Renewable-energy incentives, wind and solar development credits, renewable-energy equipment exemptions, and alternative-energy research credits should be reviewed before year-end.
• Agriculture, tribal, and Native American jurisdiction issues can affect income, withholding, sales, property, and incentive analysis.
• Quality Jobs, investment, manufacturing, aerospace, agriculture, technology, software, data-center, and energy incentives should be reviewed before year-end.
• Disaster relief should be verified by county, tax type, taxpayer category, and postponed date.

Instead AI helps tax teams treat Oklahoma due dates as operational work, not a static checklist.

Tax-professional context: Oklahoma's 2027 landscape pairs a graduated individual income tax with separate corporate and pass-through filings and an energy-driven economy that layers industry-specific rules on top of the core return calendar. For tax year 2027 Oklahoma uses a three-bracket graduated individual income tax with a 4.5% top rate, and it continues to offer a state Earned Income Credit and a range of business incentives.

Electronic filing requirements:

• C Corporations and pass-through entities should file and pay through the Oklahoma Taxpayer Access Point (OkTAP).
• Individuals can e-file through Oklahoma's online system; the April 20, 2028 timing applies only when the return is e-filed and paid electronically by the required date.
• Professional preparers must use approved software vendors.

Business Tax Credits:

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

Retirement income considerations:

• Military retirement pay may be exempt from Oklahoma income tax.
• Social Security benefits are generally exempt.
• Pension income and senior-citizen benefits — review against current Form 511 instructions.

Oklahoma's multi-bracket individual rate and separate entity forms reward specialist review from the accounting firm directory.

What sources support these Oklahoma dates?

• Oklahoma Tax Commission Help Center.
• Oklahoma Form 512 corporation instructions.
• Oklahoma Form 514 partnership instructions.
• Oklahoma Form 512-S S Corporation instructions.

Keep Oklahoma federal-plus-30 deadlines straight

Instead's AI-driven tax platform helps Oklahoma teams coordinate return work, payment review, extensions, and filing follow-through before deadlines move from planning to execution.

For Oklahoma practices, planning, estimates, and multi-entity help connect research, planning, and operational handoffs without duplicating deadline data. Built for tax professionals who want source-backed state deadline control across clients, entities, and reviewer workflows.