October 2026 Business Tax Due Dates

October brings several key tax deadlines for businesses and self-employed professionals. Be sure to review these upcoming filing, payroll tax deposit, and retirement plan deadlines to ensure your business remains compliant and avoids unnecessary penalties.

October 15: Corporate Tax Returns

Corporations must file their 2025 calendar year income tax return (Form 1120) and pay any resulting tax, interest, and penalties due. Please note that this specific due date applies only if your business timely requested an automatic six-month extension by April 15.

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

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

October 15: Nonpayroll Withholding

Similarly, if the monthly deposit rule applies to your nonpayroll withholding, you must deposit the tax for September payments by this date.

Self employed business owner reviewing schedule

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, marks 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

This date is also the final deadline to actually contribute to a SEP IRA or Keogh retirement plan for the 2025 calendar year, provided your tax return is on extension through October 15.

Weekend and Holiday Adjustments

As a general rule for tax deadlines, if a 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 Extensions

When a geographical area is federally designated as a disaster area, tax due dates are typically extended to provide relief. To check if your region has been designated as a disaster area and to find information on specific filing extension dates, visit the following resources:

Manage Your October Tax Deadlines Effectively

Staying ahead of corporate extensions, payroll deposits, and retirement contributions is essential for maintaining your financial health as the year winds down. If you need assistance navigating these due dates or evaluating your tax planning strategy, schedule a consultation with our team today.

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