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

While January and February are often spent gathering documents, March is when the tax season truly accelerates for business owners. For our clients—particularly those running Partnerships or S Corporations in St Louis and beyond—this month marks a critical transition from preparation to filing.

March 2026 brings a convergence of deadlines for pass-through entities, information reporting, and payroll compliance. Below is your strategic roadmap to navigating these dates and maintaining compliance.

March 2: The Information Reporting Threshold

For businesses that still file on paper, early March is the cutoff. However, regulatory trends are pushing almost everyone toward electronic filing (which has a later deadline). If you are legally required or choose to file on paper, here is what is due.

Information Returns (Forms 1099 & 1096)

If you have not transitioned to e-filing yet, you must file the government copies of various 1099 forms (excluding the 1099-NEC, which was due previously) along with the transmittal Form 1096. This covers payments made in 2025.

ACA Reporting for Applicable Large Employers (ALEs)

Employers categorized as ALEs must file paper Forms 1094-C and 1095-C. Other providers of minimum essential coverage must file Forms 1094-B and 1095-B. Please note: if you file these electronically, your deadline automatically shifts to March 31.

You must also furnish the recipient copies (Forms 1095-B or 1095-C) to employees and responsible individuals by this date.

Business owner reviewing tax documents

Additional Paper Filing Deadlines:

  • Gambling Winnings: File Form 1096 and Copy A of Forms W-2G.

  • Large Food & Beverage Establishments: File Form 8027 for tip income reporting.

  • Farmers and Fishermen: File your 2025 Form 1040 and pay tax due, unless you paid estimated taxes by mid-January.

March 16: The Pass-Through Entity Deadline

This is the most significant date in March for many of our business clients. It is the filing deadline for flow-through entities, meaning the results of these returns determine what is reported on your personal 1040.

Partnerships (Form 1065)

You must file the 2025 calendar year return and provide each partner with their Schedule K-1. This form details the partner's share of income, deductions, and credits. If the return is not ready, we strongly advise filing Form 7004 to secure an automatic 6-month extension. This extends the filing deadline to September 15, though it does not extend the time to pay any taxes owed.

S Corporations (Form 1120-S)

Similar to partnerships, S Corps must file their 2025 income tax return and issue Schedule K-1s to shareholders. If you need more time to ensure accuracy, filing Form 7004 provides a 6-month extension. Note that S Corps must also pay any tax due by this date to avoid interest and penalties, even if an extension is filed.

S Corporation Election (Form 2553)

If you operate an LLC or C Corp and wish to be taxed as an S Corp for the 2026 calendar year, you must file Form 2553 by March 16. Missing this window generally means the election won’t take effect until 2027, potentially costing you significant self-employment tax savings.

Tax planning and strategy documents

March 31: The E-Filing Deadline

The IRS encourages electronic filing for accuracy and efficiency. If you file the following forms electronically, you gain extra time until the end of the month:

  • Forms 1099, 1098, and W-2G: This is the final electronic filing due date.

  • ACA Forms (1094-C, 1095-C, 1094-B, 1095-B): Electronic submission deadline.

  • Form 8027: For large food and beverage establishments filing digitally.

Disaster Area Extensions

Unforeseen events can disrupt business operations. When a geographical area is designated as a federal disaster area, tax deadlines are often extended to provide relief. We monitor these announcements closely for our clients.

To check if your area is affected, please verify via the official channels:

FEMA: https://www.fema.gov/disaster/declarations
IRS: https://www.irs.gov/newsroom/tax-relief-in-disaster-situations

A Note on Weekends & Holidays
Remember, if a due date falls on a weekend or legal holiday, it automatically rolls to the next business day.

Managing these deadlines is about more than avoiding penalties; it is about ensuring your financial data is accurate so you can make informed decisions for the rest of 2026. If you need assistance with an extension or have questions about S Corp elections, please contact our office.

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