Top 10 Tax Deadlines Every Oklahoman Should Know
Stay ahead of important tax deadlines with our comprehensive guide to federal and Oklahoma state tax due dates. Missing these deadlines can result in costly penalties and interest charges.
Don't Risk Penalties!
The IRS and Oklahoma Tax Commission impose significant penalties for late filing and payment. Some penalties can be 25% or more of taxes owed. Mark these dates in your calendar now!
The 10 Most Important Tax Deadlines
1. January 31
CriticalForm 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.
Penalty for missing: $50-$280 per form, plus interest
2. March 15
BusinessS-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.
Extension available: Until September 15 (federal) / October 15 (Oklahoma)
3. April 15
CriticalIndividual 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.
Extension available: Until October 15 (filing only, not payment)
4. May 15
FilingTax-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.
Extension available: Until November 15 (6-month extension)
5. June 15
QuarterlySecond 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.
Safe harbor: Pay 100% of prior year tax (110% if AGI > $150K)
6. September 15
QuarterlyThird 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).
Note: Plan ahead for year-end tax strategies
7. October 15
ExtendedExtended 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.
Important: Taxes must still be paid by original due date to avoid interest
8. December 31
Year-EndYear-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.
Key strategies: Equipment purchases, expense acceleration, charitable giving
9. January 15 (Following Year)
QuarterlyFourth 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.
Alternative: File return and pay balance due by January 31
10. Various Dates
PayrollPayroll 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.
Penalty: Up to 15% of unpaid taxes for late deposits
Special Oklahoma Considerations
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
Oklahoma Tax Commission Specifics:
- Electronic filing required for most business returns
- Different extension deadlines for some business entities
- Installment agreement options available for unpaid taxes
- First-time penalty abatement available in some cases
Planning Calendar Template
Create a tax calendar with these key dates. Set reminders 30 days before each deadline to ensure adequate preparation time.
Monthly Reminders:
- • Payroll tax deposits
- • Sales tax filing (if applicable)
- • Bookkeeping updates
- • Receipt organization
Quarterly Tasks:
- • Estimated tax payments
- • Form 941 filing
- • Financial statement review
- • Tax planning adjustments
Penalties for Missing Deadlines
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
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
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
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
Professional Reminder Service
At Klingeman CPAs, we maintain a comprehensive deadline calendar for all our clients. We provide advance reminders and handle filings to ensure you never miss a critical deadline. Our former IRS experience helps us navigate compliance requirements and minimize penalties when issues arise.
Take Action Now
Don't wait until the last minute. Here's what to do immediately:
- Create your tax calendar with all relevant deadlines
- Set up automatic reminders 30 days before each deadline
- Organize your current tax documents and catch up on any missing filings
- Consider professional help if you're behind or overwhelmed
- Establish quarterly check-ins to review upcoming deadlines
Remember: staying compliant with tax deadlines isn't just about avoiding penalties—it's about maintaining good standing with tax authorities and protecting your business reputation.
This deadline guide is based on current tax law and is updated regularly by the experienced team at Klingeman CPAs.