The March 16, 2026 Deadline: What It Covers
If you own an S-Corporation or a partnership, March 16, 2026 is one of the most important dates on your tax calendar. This is the original due date for:
- Form 1120-S — the U.S. Income Tax Return for an S Corporation
- Form 1065 — the U.S. Return of Partnership Income
- Schedule K-1s — which must be distributed to all shareholders (S-Corps) or partners (partnerships) by this same date
Note: March 15 is the statutory deadline, but it falls on a Sunday in 2026, so the actual deadline shifts to Monday, March 16, 2026.
Why the March Deadline Matters More Than You Think
Most individual taxpayers think of April 15 as "tax deadline day." But for pass-through entity owners, March 16 is more consequential — and missing it has downstream effects on your personal return.
Here's why: S-Corps and partnerships file informational returns and issue Schedule K-1s that report each owner's share of income, deductions, and credits. Your personal return (Form 1040) cannot be completed accurately until you receive your K-1. This means:
- If your S-Corp or partnership files late, you can't complete your personal return on time.
- You may be forced to file a personal extension (Form 4868) even if your personal return is otherwise ready.
- Late K-1s are a leading cause of amended individual returns.
The March 16 deadline exists specifically to give pass-through entity owners enough time to complete their personal returns by April 15.
What's Actually Due on March 16
Form 1120-S (S-Corporations)
Form 1120-S reports the S-Corporation's income, deductions, and credits for the year. The return itself does not result in a tax payment (S-Corps are pass-through entities — income is taxed at the shareholder level). However, the return must be filed or extended on time, and Schedule K-1s must be distributed to all shareholders.
Key items on 1120-S:
- Ordinary business income or loss
- Rental income and other separately stated items
- Section 179 deductions and bonus depreciation
- Shareholder W-2 wages (reasonable compensation)
- Accumulated Adjustments Account (AAA)
Form 1065 (Partnerships and Multi-Member LLCs)
Form 1065 is the informational return for general partnerships, limited partnerships, LLPs, and multi-member LLCs taxed as partnerships. Like the 1120-S, no entity-level tax is paid with the return (unless the partnership has New Jersey BAIT obligations).
Key items on 1065:
- Ordinary income or loss from partnership activities
- Guaranteed payments to partners
- Section 704(b) allocations if partners have special allocation agreements
- Self-employment income allocations for general partners
Schedule K-1s
This is the document each owner receives from the entity. It shows your individual share of income, deductions, and credits. K-1s must be distributed by the same March 16 deadline.
If you have multiple K-1s (e.g., you're a partner in multiple partnerships or an investor in several S-Corps), all of them should be in your hands before you can finalize your personal return.
New Jersey-Specific Considerations
New Jersey has its own pass-through entity requirements that align with (but are not identical to) federal due dates.
NJ CBT-1065 and NJ-1065
New Jersey requires partnerships to file Form NJ-1065, which is due on the same date as the federal return — March 16 for most partnerships in 2026. The NJ-1065 includes a New Jersey Gross Income Tax prepayment for non-resident partners.
NJ BAIT Election
The New Jersey Business Alternative Income Tax (BAIT) allows pass-through entities to elect to pay income tax at the entity level. This election must be made annually and is due by March 16 for tax year 2025 (or with the entity return). The BAIT election can significantly benefit partners and shareholders by effectively bypassing the federal SALT deduction cap.
NJ-CBT-100S (S-Corporations)
S-Corporations in New Jersey must file Form NJ-CBT-100S and pay NJ Corporation Business Tax. Unlike federal S-Corp treatment (where no entity-level tax is owed), New Jersey imposes a minimum tax and potentially additional CBT tax on S-Corps. This is a common surprise for business owners who assume their S-Corp has no state-level tax obligations.
What If You Can't File by March 16?
File an extension. The IRS automatically grants a 6-month extension if you file Form 7004 by March 16. For S-Corps, this extends the deadline to September 15, 2026. For partnerships, same — September 15, 2026.
Important: An extension of time to file is not an extension of time to pay. If your entity owes any taxes (some S-Corps owe built-in gains tax or excess net passive income tax), those amounts are still due by March 16. Underpayment can result in penalties and interest.
NJ extension: New Jersey also requires a separate state extension. NJ Form CBT-200-T (for corporations) or the NJ-1065 extension request must be filed with NJ by the original due date.
Late Filing Penalties
The IRS imposes penalties for late filing of pass-through entity returns:
- Form 1065 (Partnerships): $245 per partner, per month (up to 12 months maximum) — so a 3-partner LLC that files 3 months late could face $2,205 in penalties.
- Form 1120-S (S-Corps): $245 per shareholder, per month (up to 12 months maximum).
These penalties can add up quickly for multi-partner arrangements. Filing an extension eliminates the late-filing penalty, even if you can't pay what's owed.
Action Items for Business Owners
If you own an S-Corp or partnership and have not yet engaged a CPA for your 2025 return, here's what to do right now:
- Gather your 2025 financials. P&L statement, balance sheet, and bank reconciliations for the full year.
- Compile payroll records. W-2s for all employees, including owner-employees (S-Corp shareholders who received wages).
- Pull last year's return. Your 2024 1120-S or 1065 provides carry-forward items, basis schedules, and depreciation records.
- Contact a CPA now. The March 16 deadline is approaching fast. If your return can't be completed in time, a CPA can file Form 7004 to buy you six additional months.
Monaco CPA handles S-Corp and partnership returns for New Jersey small businesses. Contact us to discuss your situation.
Greg Monaco, CPA, MBA is the founder of Gregory Monaco, CPA LLC, a virtual CPA practice based in Livingston, NJ. His practice focuses on small business tax compliance, S-Corp elections, and NJ tax planning. Member of AICPA and NJSCPA.
