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

If January was the warm-up, March is the main event for many business owners. While the individual tax deadline in April gets the most media attention, March 2026 is arguably the most critical month for pass-through entities and employers.

This month, we are looking at major filing deadlines for Partnerships and S Corporations, as well as the final push for information reporting. Missing these dates can trigger a cascade of late fees and delay the issuance of Schedule K-1s to your partners and shareholders—which in turn delays their personal filings.

Here is your roadmap for navigating the March 2026 business tax landscape.

Business owner reviewing tax documents with coffee

March 16: The Big Deadline for Pass-Through Entities

Because March 15, 2026, falls on a Sunday, the deadline for calendar-year Partnerships and S Corporations moves to Monday, March 16. This is the date to file your federal return or request an extension.

Partnerships (Form 1065)

Partnerships must file Form 1065 and provide each partner with their Schedule K-1. This schedule reports the partner's share of income, deductions, and credits. If you have international relevance, don't forget the potential requirement for Schedule K-3.

Need more time? You can file Form 7004 to request an automatic 6-month extension. This pushes the filing deadline to September 15, giving you breathing room to ensure accuracy. Remember, an extension to file is not an extension to pay any state-level taxes that might be due.

S Corporations (Form 1120-S)

Similar to partnerships, S Corps must file Form 1120-S and distribute Schedule K-1s to shareholders by March 16. If your S Corp owes any tax (which can happen at the entity level in certain scenarios, or for specific state taxes), it must be paid by this date to avoid interest and penalties.

Filing Form 7004 generally grants a 6-month extension for S Corp returns as well. If you are waiting on bookkeeping clean-up or third-party documents, taking the extension is often a smarter strategic move than rushing a return that requires later amendment.

Making the 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, March 16 is generally your deadline to file Form 2553. Filing this timely ensures your S Corp status is retroactive to January 1, 2026. If you miss this window, your election generally won't take effect until 2027 unless you qualify for specific relief provisions.

Advisor consulting with business client

March 2 vs. March 31: Information Returns

The deadlines for filing information returns (like the 1099 series) depend heavily on how you file. The IRS strongly encourages electronic filing, rewarding e-filers with a later deadline.

March 2: The Paper Deadline

If you are still filing paper forms, your deadline is earlier. By March 2, you must file the following with the IRS:

  • Forms 1099 and 1096: For payments made in 2025 (excluding the 1099-NEC, which was due previously).
  • Gambling Winnings: Form 1096 and Copy A of Forms W-2G.
  • ACA Forms (1094-B/C and 1095-B/C): For Applicable Large Employers (ALEs) and providers of minimum essential coverage filing on paper.
  • Tip Reporting: Form 8027 for large food and beverage establishments.

March 31: The E-Filing Deadline

If you file these forms electronically, you gain nearly an extra month. The deadline extends to March 31 for electronic submissions of Forms 1099, 1098, W-2G, 8027, and the ACA forms (1094/1095). Given the efficiency and lower error rate, we recommend e-filing for almost all clients.

Other Notable Deadlines

March 2: Farmers and Fishermen

If you didn't pay your estimated taxes by January 15, your 2025 income tax return (Form 1040) is due by March 2 to avoid penalties. If you did make that January payment, you can wait until the standard April 15 deadline.

March 16: Monthly Payroll & Withholding

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

Extensions and Disaster Relief

Tax compliance isn't just about dates; it's about geography. If your business is located in a federally designated disaster area, you may have automatic extensions available to you. Always verify your status on the IRS Tax Relief page.

Managing business due dates requires precision. Whether you need to file an extension for your partnership or finalize your S Corp election, we are here to ensure you stay compliant without the stress.

Contact us today to schedule your review.

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