October 2026 Business Tax Due Dates

October brings several key tax deadlines for businesses and self-employed professionals. As we head into the fall, it is a great time to review your upcoming filing obligations, payroll tax deposits, and retirement plan deadlines to ensure everything stays on track.

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October 15: Corporate Income Tax Returns

If your corporation requested an automatic six-month extension back by April 15, your 2025 calendar year income tax return (Form 1120) is now due. You must file the return and pay any remaining tax, interest, and penalties owed by this date.

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

If your business falls under the monthly deposit rule, October 15 is the deadline to deposit the tax for payments made during September.

October 15: Nonpayroll Withholding

Similarly, if the monthly deposit rule applies to your nonpayroll withholding obligations, you must deposit the tax for any September payments by this mid-month deadline.

October 15: Establishing a Keogh Account for 2025

For self-employed individuals who received an automatic six-month extension of time to file their 2025 tax return, October 15, 2026, serves as the final day to establish a Keogh Retirement Account if you intend to make a contribution for the 2025 tax year.

October 15: SEP IRA and Keogh Contributions

If your tax return is on extension through October 15, this is also your last day to actually contribute to a SEP IRA or Keogh retirement plan for the 2025 calendar year.

Weekend and Holiday Rule

As a general reminder, whenever a standard tax due date falls on a Saturday, Sunday, or legal holiday, the deadline is automatically extended to the next business day that is not a legal holiday.

Disaster Area Tax Extensions

Filing and payment deadlines are frequently extended when a specific geographical area is designated as a federal disaster area. For the latest information on whether your region—in California or elsewhere—has received a disaster designation and qualifies for filing extension dates, verify directly through these official resources:

FEMA: https://www.fema.gov/disaster/declarations
IRS: https://www.irs.gov/newsroom/tax-relief-in-disaster-situations

Keep Your Business Compliant This October

Meeting these mid-October deadlines keeps your business running smoothly and helps you avoid unnecessary penalties. If you have questions about your payroll deposits, retirement contributions, or extended corporate returns, the team at Christiansen Accounting is here to help. Reach out to schedule a consultation with us today to stay on top of your financial obligations.

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