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Key October 2026 Tax Deadlines for Businesses and the Self-Employed

October brings a critical set of tax deadlines for business owners and self-employed professionals. Taking the time to review upcoming filing requirements, payroll tax deposits, and retirement plan deadlines ensures your organization stays compliant and avoids unnecessary penalties. Below is a breakdown of the key dates you need to mark on your calendar for this month.

October 15: Corporate Income Tax Returns

If your corporation operates on a calendar year and you timely requested an automatic six-month extension by April 15, your deadline has arrived. You must file your 2025 income tax return (Form 1120) by October 15, 2026. Be sure to pay any tax, interest, and penalties due at this time.

Business paperwork and tax forms

October 15: Payroll and Nonpayroll Withholding Deposits

Employers and businesses subject to the monthly deposit rule must deposit their taxes for payments made in September. This October 15 deadline applies to Social Security, Medicare, and withheld income tax, as well as nonpayroll withholding.

October 15: SEP IRA and Keogh Retirement Accounts

Self-employed individuals who received an automatic six-month extension of time to file their 2025 tax returns face a strict deadline for retirement planning. October 15, 2026, is the final day to establish a Keogh retirement account if you intend to make a contribution for the 2025 calendar year. It is also the last day to actually fund your SEP IRA or Keogh plan for the 2025 tax year while your return is on extension through October 15.

Extensions for Weekends, Holidays, and Disaster Areas

Deadlines are generally rigid, but a few exceptions apply. If a due date falls on a Saturday, Sunday, or legal holiday, your deadline is automatically extended to the next business day that is not itself a legal holiday.

Additionally, businesses located in geographically designated disaster areas will receive extended due dates. To check if your area qualifies for relief and to find specific filing extension dates, review the official declarations on the following websites:

Tax professional advising a client

Manage Your Business Deadlines with Confidence

Navigating extensions, payroll rules, and retirement funding requires careful organization as the year begins to wind down. If you need assistance finalizing your corporate return or ensuring your payroll deposits remain compliant, schedule a consultation with our tax professionals today.

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