Top 10 Tax Deadlines Every Oklahoman Should Know

The 10 Most Important Tax Deadlines

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• January 31
  • Form W-2 and 1099 Distribution

Employers must provide W-2s to employees and 1099s to contractors. This is also the deadline for fourth quarter payroll tax deposits and annual unemployment reports.

Who's affected: All employers and businesses with contractors Penalty for missing: $50-$280 per form, plus interest

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• March 15
  • S-Corp and Partnership Tax Returns

S-Corporations (Form 1120S) and Partnerships (Form 1065) must file their tax returns or request an extension. Oklahoma follows the same deadline for state returns.

Who's affected: S-Corps, partnerships, and multi-member LLCs Extension available: Until September 15 (federal) / October 15 (Oklahoma)

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• April 15
  • Individual Tax Returns & First Quarter Estimates

The most well-known deadline: individual tax returns (Forms 1040 and 511-OK) and first quarter estimated tax payments are due. Also the deadline for prior-year IRA contributions.

Who's affected: All individual taxpayers Extension available: Until October 15 (filing only, not payment)

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• May 15
  • Tax-Exempt Organizations (Form 990)

Nonprofit organizations must file Form 990, 990-EZ, or 990-N depending on their size and revenue. Oklahoma requires concurrent filing of Form 511-X.

Who's affected: 501(c)(3) and other tax-exempt organizations Extension available: Until November 15 (6-month extension)

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• June 15
  • Second Quarter Estimated Tax Payments

Individuals and businesses making quarterly estimated tax payments must make their second quarter payment to both federal and Oklahoma tax authorities.

Who's affected: Self-employed individuals, business owners, investors Safe harbor: Pay 100% of prior year tax (110% if AGI > $150K)

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• September 15
  • Third Quarter Estimated Tax Payments

Third quarter estimated tax payments are due. This is also the deadline for extended S-Corp and partnership returns (federal only

• Oklahoma extended deadline is October 15).

Who's affected: Quarterly taxpayers and extended business returns Note: Plan ahead for year-end tax strategies

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• October 15
  • Extended Individual & Corporate Returns

Final deadline for extended individual tax returns (Forms 1040 and 511-OK) and extended corporate returns. No further extensions available for individuals.

Who's affected: Taxpayers who filed extensions Important: Taxes must still be paid by original due date to avoid interest

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• December 31
  • Year-End Tax Planning Deadline

Last day to implement most tax strategies for the current year: equipment purchases, retirement contributions, expense timing, and income deferral strategies.

Who's affected: All taxpayers Key strategies: Equipment purchases, expense acceleration, charitable giving

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• January 15 (Following Year)
  • Fourth Quarter Estimated Tax Payments

Final quarterly estimated tax payment for the previous tax year. Many taxpayers prefer to file their return early instead of making this payment.

Who's affected: Quarterly taxpayers Alternative: File return and pay balance due by January 31

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• Various Dates
  • Payroll Tax Deposits

Federal payroll tax deposits are due either semi-weekly (Wednesday/Friday) or monthly (15th of following month) based on deposit schedule. Oklahoma withholding follows federal schedule.

Who's affected: All employers Penalty: Up to 15% of unpaid taxes for late deposits

Special Oklahoma Considerations

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Oklahoma-Specific Deadlines:

• Sales Tax Returns: Due 20th of the month following the reporting period

• Use Tax Returns: Due with income tax return (April 15 or extended deadline)

• Business Personal Property: March 15 (annual filing)

• Motor Vehicle Registration: Birthday month of owner

Penalties for Missing Deadlines

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Federal Penalties:

• Late Filing: 5% per month (maximum 25%)
• Late Payment: 0.5% per month (maximum 25%)
• Failure to Pay Estimated Tax: Calculated based on underpayment amount
• Payroll Tax Penalties: 2-15% depending on how late

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Oklahoma Penalties:

• Late Filing: 5% per month with $25 minimum
• Late Payment: 1% per month
• Underpayment Interest: Variable rate based on federal short-term rate

Tips for Staying Compliant

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Organization Strategies:

• Use Technology: Set up calendar reminders with 30-day advance notice
• Automate When Possible: Electronic payments and filing reduce errors
• Maintain Good Records: Organized books make filing easier and faster
• Work with Professionals: CPAs can handle deadlines and optimize strategies

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Emergency Procedures:

• If You're Behind: File extensions immediately to avoid failure-to-file penalties
• Payment Plans: Both federal and state offer installment agreements
• Professional Help: CPAs can negotiate penalty abatements and payment plans