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March 2026 Business Tax Calendar: S Corps, Partnerships, and Reporting Deadlines

For many of our clients at Integrated Accounting Solutions, March represents a critical juncture in the financial calendar. While January and February focus heavily on payroll and issuing forms to contractors, March is when the major flow-through entities—Partnerships and S Corporations—face their filing deadlines. It is a busy time, but with our Bookkeeping and Controller Services teams supporting you, it doesn’t have to be stressful.

Below is your essential roadmap for March 2026 compliance. Keeping these dates on your radar ensures you avoid penalties and maintain the financial clarity needed to grow your business.

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March 2: The Paper Filing Deadline

While we strongly encourage electronic filing for efficiency and accuracy, if your business still files paper returns for information reporting, this is your cutoff. Because March 1 falls on a Sunday in 2026, these deadlines move to Monday, March 2.

Information Returns (Forms 1099 & 1096)

If you are filing paper copies with the IRS, you must submit Forms 1099 (for payments made in 2025) along with the transmittal Form 1096 by this date. Note that this applies to forms other than the 1099-NEC, which was due earlier in the year.

Healthcare Reporting (ACA Forms)

Applicable Large Employers (ALEs) filing paper Forms 1094-C and 1095-C must submit them to the IRS now. Similarly, other providers of minimum essential coverage filing paper Forms 1094-B and 1095-B face this deadline. If you are handling these electronically, you have until the end of the month.

Gambling Winnings & Tip Reporting

For businesses in specific sectors, paper filing deadlines also apply to:

  • Gambling Winnings: Form 1096 and Copy A of Forms W-2G.
  • Large Food/Beverage Establishments: Form 8027 (Employer’s Annual Information Return of Tip Income) and transmittal Form 8027-T.

Note: If you are filing any of the above forms electronically, your deadline is automatically extended to March 31.

Farmers and Fishermen

If you did not pay your estimated tax by January 15, you must file your 2025 income tax return (Form 1040 or 1040-SR) and pay all tax due by March 2 to avoid penalties.

March 16: The Major Business Deadline

This is the most significant date on the March calendar for many small-to-mid-sized businesses. Because March 15 falls on a Sunday, the deadline pushes to Monday, March 16.

Partnerships (Form 1065)

Calendar-year partnerships must file Form 1065 and provide Schedule K-1s to partners. This Schedule reports the partner’s share of income, deductions, and credits, which flows into their personal returns.

S Corporations (Form 1120-S)

S Corps must file the 2025 income tax return (Form 1120-S) and pay any tax due. Like partnerships, you must provide Schedule K-1s to your shareholders. This is often where our Controller Services prove invaluable—ensuring that your internal controls and reporting were accurate throughout the year so this filing is seamless.

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Need More Time? (Extensions)

If your books aren't quite ready, you can request an automatic 6-month extension by filing Form 7004. However, it is vital to remember that an extension to file is not an extension to pay. You must estimate and pay any tax owed by March 16 to avoid interest and penalties. The extended filing deadline will be September 15.

S Corporation Election (Form 2553)

If you are operating as an LLC or C Corp and want to be taxed as an S Corp for the 2026 tax year, you must file Form 2553 by March 16. If you miss this window, the S Corp treatment generally won't begin until the 2027 tax year.

Payroll & Withholding

For employers on the monthly deposit schedule, this is the due date to deposit Social Security, Medicare, and withheld income tax for February payments.

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March 31: Electronic Filing Deadline

For businesses that utilize e-filing (which is the standard for most IAS clients), this is the final due date for filing the following with the IRS:

  • Forms 1099 (except 1099-NEC) and 1096
  • Forms W-2G
  • ACA Forms (1094-C, 1095-C, 1094-B, and 1095-B)
  • Form 8027 for tip reporting

Important Administrative Notes

Weekend & Holiday Rule

Whenever a tax deadline falls on a Saturday, Sunday, or legal holiday, the due date is delayed until the next business day.

Disaster Area Extensions

If your business is located in a federally designated disaster area, the IRS may grant automatic extensions. We monitor these closely for our clients, but you can also verify the status of your area using the official links below:

Ready to focus on your business, not your books?
If these deadlines feel overwhelming, it might be time to upgrade your financial support. From basic bookkeeping to Fractional CFO guidance, Integrated Accounting Solutions is here to provide the peace of mind you deserve. Contact us today to ensure you are ready for every deadline.

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