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March 2026 Tax Calendar: Critical Deadlines for Partnerships and S Corps

For many business owners, March is when tax season truly accelerates. While individual taxpayers are eyeing April, pass-through entities—specifically Partnerships and S Corporations—are on the clock right now. Because the income from these entities flows through to the owners' personal returns, getting these business filings done (or extended) is the first domino that needs to fall.

Beyond the major income tax returns, March 2026 also marks the final cutoff for various information returns if you are e-filing. Below is your strategic roadmap for the month.

March 16: The Big Deadline for Pass-Through Entities

If your business is structured as a Partnership or an S Corporation, your federal income tax return is due. This date is critical because your partners and shareholders generally cannot file their personal Forms 1040 until they receive their Schedule K-1s from the business.

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Partnerships (Form 1065)

You must file the 2025 calendar year return (Form 1065) and provide each partner with their Schedule K-1. This schedule details their share of income, deductions, and credits. If relevant to your operations, you must also provide Schedule K-3 regarding international tax items.

S Corporations (Form 1120-S)

Similar to partnerships, S Corps must file Form 1120-S and pay any tax due. Each shareholder must receive their Schedule K-1 (and Schedule K-3, if applicable) to complete their personal tax filings.

Need More Time? File an Extension

If your books aren't quite ready, or you are waiting on lagging corrections, do not panic. You can request an automatic 6-month extension by filing Form 7004. If you file this by March 16, your new deadline becomes September 15. However, please note that an extension to file is not an extension to pay. If the S Corp owes any tax, it must be estimated and paid by March 16 to avoid penalties.

March 16: Strategic S Corp Elections

For Limited Liability Companies (LLCs) or C Corporations looking to change their tax treatment, this is a pivotal date. You must file Form 2553 (Election by a Small Business Corporation) by March 16 if you want to be taxed as an S Corp for the calendar year 2026. If you miss this window, the election generally won't take effect until 2027, potentially delaying significant tax savings on self-employment taxes.

March 2: The "Paper Filing" Deadline

While the IRS strongly encourages—and in many cases mandates—electronic filing, there are still deadlines for those filing on paper. If you are mailing physical forms, March 2 is your due date for:

  • Information Returns: Government copies of Form 1096 and certain 1099s (excluding the 1099-NEC, which was due in January).
  • Gambling Winnings: Form 1096 and Copy A of Forms W-2G.
  • ACA Forms: Applicable Large Employers (ALEs) filing paper Forms 1094-C and 1095-C, and other providers filing 1094-B and 1095-B.
  • Tip Reporting: Large food and beverage establishments filing Form 8027 (and 8027-T if applicable).

Farmers and Fishermen: If you did not pay your estimated taxes by January 15, your 2025 income tax return (Form 1040) is due March 2 to avoid penalties. If you did pay estimates early, you can wait until April 15.

March 31: The Electronic Filing Deadline

One of the primary benefits of e-filing—aside from security and tracking—is the extra time it affords you. If you file electronically, the deadline for the following forms is extended to March 31:

  • Forms 1098 and 1099 (other than 1099-NEC)
  • Forms W-2G (Gambling Winnings)
  • ACA Forms 1094-C, 1095-C, 1094-B, and 1095-B
  • Form 8027 (Tip Income)
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Other Routine Deadlines

March 16: Monthly Deposits

For businesses adhering to the monthly deposit rule, payments for Social Security, Medicare, and withheld income tax for February are due. This also applies to non-payroll withholding.

Health Coverage Reporting

By March 2, Applicable Large Employers must provide Forms 1095-C to full-time employees, and other coverage providers must issue Forms 1095-B to responsible individuals.

Extensions and Special Circumstances

Weekends & Holidays: It is standard IRS practice that if a due date falls on a Saturday, Sunday, or legal holiday, the deadline is pushed to the next business day.

Disaster Relief: The IRS frequently offers automatic extensions to businesses located in federally declared disaster areas. If your business has been impacted by severe weather, verify your status below:

If you are concerned about getting your K-1s out on time, or if you need to discuss the pros and cons of an S Corp election for 2026, please contact our office immediately. We can handle the extensions to ensure you remain compliant while we finalize the numbers.

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