March 2026 Business Tax Calendar: Critical Deadlines for Partnerships & S Corps

For many of our business clients, March represents the true peak of tax season. While April 15th gets all the media attention, March is the heavy lifting month for pass-through entities and employers wrapping up their information reporting. It’s a time of back-to-back deadlines, and missing them can lead to costly penalties.

Because several standard due dates fall on weekends in 2026, you will notice some adjustments to the usual calendar—specifically, deadlines moving to the next business day. Below is your roadmap for navigating the critical compliance dates this month.

Business Tax Deadlines Calendar

March 2, 2026: The Information Reporting Deadline

Since February 28 falls on a weekend, the deadline for several information returns and specific industry filings pushes to Monday, March 2.

Information Returns (Forms 1099 & 1096)

If you are filing paper forms, this is the due date to submit government copies of Form 1099 (excluding 1099-NEC, which was due earlier) along with the transmittal Form 1096. This applies to various payments made during 2025.

Healthcare Reporting (ACA Forms)

Applicable Large Employers (ALEs) filing paper forms must submit Forms 1094-C and 1095-C to the IRS. All other providers of minimum essential coverage filing on paper must submit Forms 1094-B and 1095-B. Note that if you file these electronically, your deadline is automatically extended to March 31.

Farmers and Fishermen

If you did not pay your estimated taxes by January 15, your 2025 income tax return (Form 1040) is due today to avoid penalties. If you made that estimated payment, you have until April 15.

Gambling Winnings & Tip Income

Casinos and similar establishments must file Form 1096 and Copy A of Forms W-2G. Large food and beverage establishments must file Form 8027 for tip income reporting. As with other forms, e-filing extends this deadline to March 31.

March 16, 2026: The Pass-Through Entity Crunch

This is arguably the most significant date on the business tax calendar. Partnerships and S Corporations must file their returns or request an extension today. Since March 15 is a Sunday, you have until Monday, March 16.

Accounting Team Meeting

Partnerships (Form 1065)

Partnerships must file their 2025 calendar year return (Form 1065) and provide Schedule K-1s to partners. If your books aren't quite ready, we must file Form 7004 to secure a 6-month extension. This extension gives you until September 15 to file the return and issue K-1s, but it does not extend the time to pay any state-level taxes that might be owed.

S Corporations (Form 1120-S)

S Corps must file Form 1120-S and issue shareholder K-1s. If you anticipate owing tax (which can happen with certain built-in gains or passive income), payment is due today. Like partnerships, you can file Form 7004 for a 6-month extension.

S Corp Election (Form 2553)

If you are an LLC or C Corp looking to be taxed as an S Corp for the 2026 tax year, you must file Form 2553 by today. Missing this window means the election generally won't take effect until 2027 unless you qualify for specific relief.

March 31, 2026: Electronic Filing Deadline

The IRS encourages e-filing by granting a later deadline. If you file Forms 1099, 1098, W-2G, or ACA forms (1094/1095) electronically, this is your final due date. Electronic filing is not only faster but significantly reduces the chance of manual processing errors.

Abstract Digital Pattern

Important Reminders

Disaster Area Extensions

If your business is located in a federally declared disaster area, you likely have automatic extensions. We monitor the FEMA and IRS announcements closely to see if these apply to you.

Need an Extension?

If you realize you won't have your data ready for the March 16 deadline, please contact our office immediately. Filing an extension is a standard procedure and is far better than filing a late or incomplete return. Let's get your extension filed to avoid unnecessary penalties.

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