Critical October 2025 Tax Deadlines for Businesses

As the crisp days of October herald the approach of winter, business owners need to navigate essential tax deadlines to ensure compliance and avoid unnecessary penalties. From corporate returns to critical payroll deposits and retirement plan setups, staying informed of these key dates is crucial.

October 15 - Corporate Tax Deadlines

Businesses operating on a calendar year should file their 2024 income tax return (Form 1120) by this date, completing any requisite payments including taxes, interests, and penalties. This deadline is only applicable if your corporation has secured a six-month extension since April 15.

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

Employers adhering to the monthly deposit schedule must deposit Social Security, Medicare, and withheld income taxes for September 2025 by October 15. This deadline also covers nonpayroll withholdings under the same monthly deposit rule.

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October 15 - Keogh Account Establishment

Self-employed individuals who obtained an automatic six-month filing extension must establish a Keogh retirement account by this date to be eligible for 2024 contributions.

October 15 - SEP IRA and Keogh Contributions

This is the last opportunity to make 2024 contributions to SEP IRA or Keogh plans if your tax return is extended to October 15.

October 31 - Quarterly Payroll Tax Filing

Form 941 for the third quarter of 2025 must be submitted, along with any outstanding tax deposits necessary under the accuracy deposit rules. For liabilities under $2,500, full payment with a timely return is acceptable. If all taxes for the quarter have been deposited timely, you gain until November 10 to file.

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October 31 - Small Employer Responsibilities

Small employers with a yearly liability above $2,500 but below this threshold for the third quarter must address any unremitted taxes by this date.

October 31 - Federal Unemployment Tax

If your federal unemployment tax due through September exceeds $500, this date is your deadline for deposit.

Weekend & Holiday Rule:

Deadlines falling on weekends or legal holidays are extended to the next business day that isn’t a holiday.

Disaster Area Extensions:

Regions designated as disaster areas receive automatic due date extensions. Check FEMA and IRS websites for updates on designated areas and adjusted filing dates.

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