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Critical March 2026 Tax Deadlines for Long Island Businesses

March acts as the definitive turning point in tax season. While individuals are gathering documents, business owners face some of the most rigorous deadlines of the year. For our clients across Long Island—from Medford to Brentwood and Mastic—this month requires careful attention to detail regarding entity filings and information reporting.

If you manage a Partnership or S Corporation, or if you still file paper information returns, the following dates are non-negotiable to avoid penalties.

March 2: The Deadline for Paper Filings and Special Industries

While electronic filing is the standard, businesses that still rely on paper forms for information reporting must adhere to this earlier deadline.

Information Returns (Paper)

If you are filing paper government copies, today is the due date for:

  • Forms 1099 and 1096: Covering payments made in 2025 (excluding the 1099-NEC, which was due previously).
  • Gambling Winnings: Form 1096 and Copy A of Forms W-2G.
  • ACA Reporting: Applicable Large Employers (ALEs) must file paper Forms 1094-C and 1095-C. Other providers of minimum essential coverage must file Forms 1094-B and 1095-B.
  • Tip Income: Large food and beverage establishments must file Form 8027 (and 8027-T if applicable).

Note: If you file these forms electronically, you generally have until March 31.

Office dog helping with tax deadlines

Farmers and Fishermen

For those in the agriculture or fishing industries who did not pay estimated taxes by January 15, your 2025 income tax return (Form 1040) is due now. Paying the tax due by this date avoids estimated tax penalties.

March 16: The Big Business Deadline (Partnerships & S Corps)

This is the primary deadline for pass-through entities. Timely filing is critical because late filing penalties for these forms are calculated per partner/shareholder, per month, which adds up rapidly.

Partnerships (Form 1065)

You must file the 2025 calendar year return (Form 1065). Crucially, you must also provide each partner with their Schedule K-1 and, if applicable, Schedule K-3. These documents allow partners to file their personal returns accurately.

S Corporations (Form 1120-S)

File the 2025 calendar year income tax return (Form 1120-S) and pay any tax due. Similar to partnerships, you must issue Schedule K-1 to each shareholder.

Need More Time?

If your books aren't ready, 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. The extended deadline for providing K-1s and filing the final return will be September 15.

Business tax documents organized in a folder

S Corporation Election

If you intend to be taxed as an S Corp beginning with the 2026 calendar year, you must file Form 2553 (Election by a Small Business Corporation) by this date. Missing this window usually means the election won't take effect until 2027.

March 31: The E-Filing Deadline

For businesses that leverage technology (which we highly recommend for efficiency and security), this is the deadline to electronically file:

  • Forms 1099, 1098, and W-2G with the IRS.
  • ACA Forms 1094-C, 1095-C, 1094-B, and 1095-B.
  • Form 8027 for tip income reporting.

Important Administrative Notes

Disaster Area Relief

The IRS frequently adjusts deadlines for areas impacted by natural disasters. If your business is located in a designated disaster zone, your filing dates may be extended automatically. You can verify your status here:

Weekend & Holiday Rule

When a due date falls on a Saturday, Sunday, or legal holiday, the deadline shifts to the next business day.

Whether you are in Medford, Mastic, or elsewhere on Long Island, missing these dates can be costly. If you need assistance filing an extension or finalizing your S Corp or Partnership returns, please reach out to our team immediately.

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