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

If January and February are the warmup act for tax professionals and business owners, March is the main event for pass-through entities. As we move deeper into the 2026 filing season, several major compliance dates converge, specifically for Partnerships and S Corporations.

Because the standard March 15 deadline falls on a Sunday this year, you have until March 16, 2026, to handle your primary business income tax returns. Getting these filed—or properly extended—is essential not just for the business, but for the individual partners and shareholders waiting on Schedule K-1s to file their own personal returns.

Here is your guide to navigating the business tax deadlines for March 2026.

Office desk with financial documents and calculator

March 2: The "Paper Filing" & Information Returns Deadline

While electronic filing is the standard for most modern businesses, specific paper filing deadlines land early in the month. Since February 28, 2026, falls on a Saturday, these deadlines push to the next business day: Monday, March 2.

Information Returns (Forms 1099 & 1096)

If you still file paper forms, this is the deadline to submit government copies of information returns (Form 1099 series) along with the transmittal Form 1096. This covers payments made in 2025, excluding the 1099-NEC forms which were due back in late January.

Healthcare Reporting (ACA Forms)

Applicable Large Employers (ALEs) filing paper forms must submit Forms 1094-C and 1095-C to the IRS. Similarly, other providers of minimum essential coverage filing on paper must submit Forms 1094-B and 1095-B. Remember, if you file these electronically, you have until March 31.

Specialized Industries

  • Farmers and Fishermen: If you did not pay your estimated taxes by January 15, your 2025 income tax return (Form 1040) is due now to avoid penalties.
  • Gambling Winnings: Casinos and other payers must file Form 1096 along with Copy A of Forms W-2G.
  • Food & Beverage: Large establishments must file Form 8027 (Tip Income) and Form 8027-T if filing by paper.

March 16: The Big Deadline for Pass-Through Entities

Because the 15th is a Sunday, Monday, March 16 is the critical date for S Corporations and Partnerships. This is often the busiest week of the year for business tax preparation.

Business partners reviewing documents in a meeting

S Corporations (Form 1120-S)

S Corps must file their 2025 calendar year income tax return and pay any tax due. Crucially, you must provide each shareholder with their Schedule K-1. Without this document, your shareholders cannot accurately file their personal income tax returns.

Need more time? You can file Form 7004 to request an automatic 6-month extension. However, 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.

Partnerships (Form 1065)

Similar to S Corps, partnerships must file their 2025 return or request an extension via Form 7004. Partners generally cannot complete their personal 1040s until they receive their Schedule K-1 (and potentially Schedule K-3 for international items) from the partnership.

S Corp Election (Form 2553)

If you operate an LLC or C Corp and want to be taxed as an S Corporation for the 2026 tax year, you must file Form 2553 by this date. Filing late means the election generally won't take effect until 2027, unless reasonable cause can be established.

March 31: Electronic Filing Deadlines

If you utilize electronic filing (which is highly recommended for accuracy and speed), your deadline for several information returns is extended to the end of the month.

  • Forms 1099, 1098, and W-2G: Final due date for electronic filing with the IRS.
  • ACA Forms (1094/1095): ALEs and coverage providers filing electronically must submit their forms by today.
  • Form 8027: Electronic filing deadline for tip income reporting.

Other Compliance Reminders

Payroll and Withholding

For businesses on a monthly deposit schedule, Social Security, Medicare, and withheld income tax for February payments are due by March 16. This also applies to non-payroll withholding.

Disaster Area Relief

The IRS frequently offers automatic extensions to businesses located in federally declared disaster areas. If your business has been impacted by severe weather events, check the FEMA declarations and IRS disaster relief pages to see if your deadlines have been postponed.

We Are Here to Help

March deadlines can feel overwhelming, especially when they dictate when you can file your personal return. Whether you need to file an extension for your partnership, finalize your S Corp election, or ensure your 1099s are compliant, we can help manage the workflow.

Let’s ensure your business stays compliant. Contact us today to review your March filing requirements.

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