2026 Tax Deadlines Every Missouri Small Business Owner Must Know
Introduction
As a small business owner in Missouri serving St. Louis, St. Charles, Lincoln, and Warren County, keeping track of tax deadlines is critical. Missing even one deadline can result in hefty penalties, interest charges, and unnecessary stress. This comprehensive guide covers all major federal and Missouri state tax deadlines for 2026 so you can stay compliant and avoid penalties.
Q1 2026 Tax Deadlines
January 31, 2026 - Fourth Quarter 2025 Estimated Tax Payment
If you're a self-employed business owner, S-Corp owner, or partner, your final estimated tax payment for 2025 is due by January 31, 2026.
January 31, 2026 - W-2 and 1099 Preparation Deadline
Employers must provide W-2 forms to employees, and businesses must provide 1099 forms to contractors. While filing is due later, having these ready by January 31 is essential for tax planning.
February 2, 2026 - Quarterly Payroll Tax Filings
Employers must file Form 941 (federal payroll tax return) for Q4 2025 if they didn't deposit taxes using EFTPS or pay them with the return.
March 2, 2026 - Federal Corporate Income Tax Returns
If your business is structured as a C Corporation, your federal income tax return (Form 1120) is due March 2, 2026 (or October 2, 2026 with an extension).
Q2 2026 Tax Deadlines
April 15, 2026 - Individual Income Tax Returns
This is the big one. April 15 is the deadline for all individual income tax returns. If you're a sole proprietor, pass-through entity owner (S-Corp, LLC, Partnership), or have income from your business, your return is due April 15.
April 15, 2026 - First Quarter 2026 Estimated Tax Payment
If you're self-employed, your Q1 2026 estimated tax payment is also due April 15.
April 20, 2026 - Form 1065 and 1120-S Deadline
Pass-through entities including partnerships, LLCs, S-Corporations, and some multi-owner businesses must file Form 1065 (Partnership) or 1120-S (S-Corp) by April 20, 2026 (or October 20 with extension).
April 30, 2026 - Missouri State Income Tax Return
Missouri state income tax returns for individuals and businesses are due April 30, 2026. This is slightly later than the federal April 15 deadline.
Q3 2026 Tax Deadlines
June 15, 2026 - Second Quarter Estimated Tax Payment
Self-employed business owners and S-Corp owners should pay their Q2 estimated taxes by June 15, 2026.
July 31, 2026 - Q2 Payroll Tax Filings
Form 941 (federal payroll tax return) for Q2 2026 is due July 31. Employers must also provide quarterly W-2 information if required.
Q4 2026 Tax Deadlines
September 15, 2026 - Third Quarter Estimated Tax Payment
Q3 2026 estimated tax payments are due September 15, 2026.
October 15, 2026 - Q3 Payroll Tax Filings
Form 941 for Q3 2026 is due October 15.
October 31, 2026 - Missouri Sales Tax Report
If your business is registered for Missouri sales tax, your monthly or quarterly sales tax report is due by October 31.
December 15, 2026 - Fourth Quarter Estimated Tax Payment
The final estimated tax payment of the year for self-employed and S-Corp owners is due December 15, 2026.
Special Considerations for St. Louis & Missouri Businesses
St. Louis Local Earnings Tax
If you have employees working in St. Louis, you need to pay St. Louis Local Earnings Tax (1.5% of wages). Payments are due quarterly and vary based on your payroll timing.
Sales Tax Nexus
Missouri has different sales tax rates depending on location. If you're selling products or certain services, understand which counties and cities have sales tax obligations.
Pro Tips to Stay on Top of Deadlines
- Use a calendar. Input all deadlines into your business calendar and set reminders 2 weeks before each date.
- Keep records year-round. Don't wait until tax season. Maintain organized books throughout the year so you're ready for deadline crunch.
- Work with a bookkeeper. A professional bookkeeper tracks deadlines and ensures you're prepared months in advance.
- File early. Don't wait until the last day. Early filing gives you time to correct any issues and potentially receive refunds faster.
- Consider extensions carefully. Filing an extension pushes the deadline to October, but estimated taxes are still due on the original dates.
Final Thoughts
Tax deadlines are non-negotiable, and penalties for missing them add up quickly. Whether you're running a business in St. Louis, St. Charles, Lincoln, or Warren County, staying on top of these 2026 deadlines is essential. The Helpful Hive helps businesses track deadlines, maintain records, and prepare taxes on time. We also offer remote services for clients outside our Missouri service areas.
Don't let tax deadlines stress you out. Schedule a consultation with The Helpful Hive to discuss tax planning and deadline management for your business.