Critical Business Tax Deadlines for October 2025

As October sweeps in with crisp autumn air, it brings along significant business tax deadlines crucial for maintaining compliance—from filing corporate returns to making payroll deposits and managing retirement plan contributions. Understanding these deadlines is essential for avoiding unnecessary penalties and ensuring smooth operations.

October 15 - Corporate Tax Returns

Corporations following the calendar year need to file their 2024 income tax return (Form 1120) and settle any due taxes, interest, or penalties. This deadline applies if a six-month extension was properly requested by April 15.

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October 15 - Payroll and Withholding Taxes

Employers subject to the monthly deposit rules must deposit Social Security, Medicare, and withheld income taxes for September 2025 by October 15. Additionally, it's the deadline for nonpayroll withholding deposits if applying the monthly rule.

October 15 - Nonpayroll Obligations
Ensure timely deposit of taxes for September payments, adhering to the monthly deposit rules.

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October 15 - Establish Keogh Accounts

For self-employed individuals who obtained a tax filing extension, this date marks the last opportunity to establish a Keogh Retirement Account with intent to contribute for the 2024 calendar year.

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October 15 - SEP & Keogh Contributions

October 15 is the final day for making contributions to a SEP or Keogh retirement plan for 2024, provided the tax return is extended to this date.

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October 31 - Quarterly Payroll Filings

Submit Form 941 for the third quarter of 2025. It’s crucial to deposit or pay any remaining tax according to accuracy-of-deposit rules. If your liability is below $2,500, a full payment with the timely return is feasible. Otherwise, taxes should have been deposited in advance of this date, and filing is extended to November 10 if deposits are compliant.

October 31 - Small Employer Deposits

Small employers must deposit any tax if their total 2025 liability exceeds $2,500 but remains under $2,500 for the third quarter.

October 31 - Unemployment Tax Deadlines

Deposit Federal Unemployment Taxes due by the end of September if the tax exceeds $500.

Adjustments for Weekends and Public Holidays

Should any of these dates coincide with a weekend or legal holiday, deadlines automatically move to the next business day.

Extensions in Disaster Areas

Disaster-related extensions apply in federally designated areas. Consult FEMA's website or the IRS's resource page for specific extensions.

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