Essential October 2025 Tax Deadlines for Businesses

October brings the chill of autumn as well as crucial tax deadlines for businesses. This month is critical for filing corporate tax returns, making payroll deposits, and contributing to retirement plans. Reviewing these deadlines can help you maintain compliance and steer clear of costly penalties.

October 15 - Corporations

If your corporation follows a calendar year, remember that October 15 is the deadline to file your 2024 income tax return (Form 1120) and settle any tax liabilities, interest, and penalties, but only if you filed for a 6-month extension by April 15.

October 15 - Social Security, Medicare, and Withheld Income Tax

For employers subject to monthly deposit rules, October 15 marks the due date for depositing Social Security, Medicare, and withheld income taxes for September 2025. Moreover, this is the deadline for nonpayroll withholding deposits for the same period if monthly deposit rules apply.

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October 15 - Nonpayroll Withholding

If the monthly deposit rule applies, ensure you complete the tax deposit for payments made in September.

October 15 - Last Day to Establish a Keogh Account for 2024

Oct. 15, 2025, is the final opportunity to set up a Keogh Retirement Account for self-employment contributions concerning 2024 if you've received an automatic 6-month filing extension.

October 15 - SEP IRA & Keogh Contributions

Contributors to SEP or Keogh plans should use this deadline as their last chance to fund for the 2024 calendar year if they’re benefitting from a tax return extension through October 15.

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October 31 - Social Security, Medicare, and Withheld Income Tax

Form 941 for the third quarter of 2025 must be filed by October 31. Cover any tax shortfall per accuracy deposit rules, or if the total liability is below $2,500, opt to remit the complete amount with a prompt return. Note: If your entire quarterly tax was paid punctually, you get until November 10 to file.

October 31 - Certain Small Employers

Small employers should make deposits for any outstanding tax if their annual burden exceeds $2,500 in 2025 but is under $2,500 for Q3.

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October 31 - Federal Unemployment Tax

Deposit taxes accumulated through September if outstanding amounts rise over $500.

Weekends & Holidays:

If a deadline occurs on a weekend or public holiday, it automatically moves to the next business day, not being a public holiday.

Disaster Area Extensions:

Regions designated as disaster areas might see extended deadlines. Check whether your location qualifies and view extended filing dates at these sites:

FEMA: FEMA Disaster Declarations
IRS: IRS Disaster Tax Relief

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