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March 2026 Business Tax Calendar: Deadlines You Can't Ignore

If you felt like February was just a warm-up, you were right. March is when tax season truly kicks into high gear for most business owners. Whether you operate out of Scottsdale, Denver, or Albuquerque, the deadlines landing this month are critical for maintaining compliance and avoiding unnecessary penalties.

For our clients at GeneralCents Accounting, this month is often dominated by flow-through entity returns and finalizing information reporting. Here is your roadmap to navigating the March 2026 business due dates.

March 2: The Paper Filing Deadline

While we always encourage electronic filing for accuracy and speed, if your business still relies on paper forms, the window closes early this month.

Information Returns (Forms 1099 and 1096)

If you are filing paper copies with the government, March 2 is the deadline for Forms 1099 (and their transmittal Form 1096) for payments made in 2025. Note that this applies to returns other than the 1099-NEC, which was due back in January. This is also the paper filing deadline for Form W-2G (gambling winnings).

ACA Reporting for Employers

Applicable Large Employers (ALEs) filing paper forms must submit Forms 1094-C and 1095-C to the IRS by this date. Smaller providers of minimum essential coverage filing on paper have the same deadline for Forms 1094-B and 1095-B. Additionally, this is the deadline to furnish the health coverage forms (1095-B or 1095-C) to your employees.

Business owner reviewing tax deadlines

Farmers and Fishermen

If you did not pay your estimated taxes by January 15, your 2025 income tax return (Form 1040) is due today to avoid penalties. If you made that estimated payment, you have until the standard April deadline.

March 16: The Main Event for Flow-Through Entities

For many of our clients utilizing our BackPocket CFO services, March 16 is the most significant date on the calendar. This is the filing deadline for Partnerships (Form 1065) and S Corporations (Form 1120-S).

Filing or Extending

You must file your 2025 calendar year return and provide Schedule K-1s to your partners or shareholders. The K-1 is crucial because your partners and shareholders cannot file their personal income tax returns until they receive it.

If you aren't ready to file, you can request an automatic 6-month extension by filing Form 7004. Please remember: an extension to file is not an extension to pay. If your S Corp or partnership owes tax, it must be estimated and paid by March 16 to stop interest from accruing.

S Corp Election (Form 2553)

Strategic tax planning often involves choosing how your business is taxed. If you want to be treated as an S Corporation for the 2026 tax year, you must file Form 2553 by March 16. Filing late generally means the election won’t take effect until 2027, so don't let this slip if you're looking to optimize self-employment taxes.

Office building in business district

March 31: The E-Filing Extension

The IRS incentives technology. If you file your information returns electronically rather than on paper, your deadline is automatically pushed to March 31. This applies to:

  • Forms 1099 and 1098: Electronic filing with the IRS.
  • ACA Forms (1094/1095): Electronic filing for ALEs and coverage providers.
  • Form 8027: Electronic filing for Large Food and Beverage establishments reporting tip income.
  • Form W-2G: Electronic filing of gambling winnings.

Other Essential Housekeeping

Payroll and Withholding

If you are on a monthly deposit schedule, March 16 is the due date to deposit Social Security, Medicare, and withheld income tax for payments made in February. This also applies to non-payroll withholding.

Weekends and Disasters

As always, if a due date falls on a weekend or legal holiday, it moves to the next business day. Furthermore, if you are in a designated disaster area—something we unfortunately see occasionally across the varied terrain of the Southwest—deadlines may be extended. Always check the FEMA and IRS disaster relief pages if you believe this applies to you.

Tax season is a marathon, not a sprint. If you need help managing these deadlines or preparing your K-1s, reach out to John Koloch and the GeneralCents Accounting team today. Let’s get your filings sorted so you can get back to business.

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