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Form 1065 and 1120-S Due Dates for 2026
Calendar-year 2025 Forms 1065 and 1120-S were due March 16, 2026. A timely Form 7004 extends filing to September 15, 2026. See IRS rules.
In brief
A calendar-year partnership or S corporation files its 2025 federal return on Form 1065 or Form 1120-S. The due date was March 16, 2026, because March 15 fell on a Sunday. A Form 7004 filed by that date generally extends the time to file to September 15, 2026. The extension does not extend the time to pay any tax due. Partners and shareholders should receive their Schedule K-1s by the same date that applies to the return.
This article is general information, not tax advice.
The general rule
The IRS uses the same timing rule for both forms.
- Form 1065 is due on the 15th day of the 3rd month after the partnership's tax year ends. That is the rule in the Instructions for Form 1065.
- Form 1120-S is due on the 15th day of the 3rd month after the S corporation's tax year ends. That is the rule in the Instructions for Form 1120-S.
For a calendar-year entity, that date is usually March 15. If the 15th falls on a Saturday, Sunday, or legal holiday, the IRS treats a return filed on the next business day as timely.
Why the 2025 calendar-year date was March 16, 2026
March 15, 2026, was a Sunday. The 2025 Form 1065 instructions state that calendar-year partnerships may therefore timely file their 2025 returns by March 16, 2026. The 2025 Form 1120-S instructions give the same March 16, 2026 date for calendar-year S corporations.
The 2026 Publication 509 tax calendar lists March 16 for both filing obligations, and September 15 for entities that timely requested a six-month extension.
Form 7004 extends the time to file, not the time to pay
File Form 7004 by the regular due date to request an automatic extension. For most partnerships and S corporations, the extension period is six months.
For a calendar-year 2025 Form 1065 or Form 1120-S, a timely Form 7004 generally moves the filing deadline to September 15, 2026. Publication 509 states that date explicitly.
The extension is only more time to file the return. It is not more time to pay tax that is due. Interest can accrue on unpaid tax from the original due date. The Form 1120-S instructions also state that any tax due must be paid by the original due date, not including extensions.
The IRS no longer sends a notice that a Form 7004 extension was approved. The Form 7004 instructions say the IRS will notify you only if the request is disallowed.
Certain partnerships that keep their books and records outside the United States and Puerto Rico have a different automatic period under the regulations discussed in the Form 7004 instructions. That is a narrow rule. Do not assume it applies.
Schedule K-1s follow the return date
The partnership or S corporation must furnish each owner a Schedule K-1, and a Schedule K-3 if it applies, by the due date of the return. Publication 509 repeats this for both March 16 and the September 15 extended date.
If you file Form 7004, the K-1 deadline moves with the return. Owners who file their own Form 1040 still have their own due dates. A late K-1 can leave those owners waiting, and a separate penalty can apply for failure to furnish a complete K-1 on time. The Form 1065 instructions describe that furnishing penalty.
Fiscal-year due dates
If the tax year does not end on December 31, do not use March 16. Use the 15th day of the 3rd month after year-end, then move to the next business day if that date is a weekend or holiday.
Examples, using the statutory rule only:
- Year ended January 31: due May 15.
- Year ended June 30: due September 15.
- Year ended September 30: due December 15.
A timely Form 7004 generally adds six months to that regular due date. Confirm weekend and holiday adjustments against the official calendar before you file.
Do not confuse Form 1120-S with Form 1120
A C corporation files Form 1120. That return is due on the 15th day of the 4th month after year-end. For a calendar-year C corporation, Publication 509 lists April 15, 2026 for the 2025 return, with an extended date of October 15, 2026 if Form 7004 is filed on time. Those dates do not apply to Form 1120-S.
State partnership and S corporation due dates can also differ from the federal date. Check the state revenue department for each state where the entity files.
What if the return is late
A late or incomplete Form 1065 or Form 1120-S can draw a penalty of $255 per partner or shareholder for each month or part of a month, for up to 12 months, when the return is due after December 31, 2025. The rate is $245 when the return was due in calendar year 2025. Those rates are published on the IRS failure to file penalty page.
The IRS often assesses that penalty on a CP162A notice. First Time Abate or other relief may apply in some cases. No outcome is guaranteed.
Filing the return stops additional months from accruing, up to the 12-month cap. Paying a penalty, or requesting relief, is a separate step.
Close the books before the deadline, or before the extension runs out
The return is only as complete as the books behind it. If bank and credit card accounts are not reconciled, the Form 1065 or Form 1120-S, and the K-1s, are not ready.
If the books are behind, count the unreconciled months and use the cleanup quote (coming soon). Catch-up work at Alignment Capital is $250 per month behind. See catch-up bookkeeping cost.
Use the deadline calendar (coming soon) to map federal due dates by entity type and year-end. For monthly bookkeeping going forward, see pricing or get started.
FAQ
When is Form 1065 due for a calendar-year partnership?
For the 2025 tax year, March 16, 2026. In a year when March 15 is a weekday and not a holiday, the date is March 15.
When is Form 1120-S due for a calendar-year S corporation?
The same date as Form 1065: March 16, 2026 for 2025 calendar-year returns.
When is the extended deadline?
September 15, 2026, for calendar-year 2025 returns, if Form 7004 was filed by the regular due date.
Does Form 7004 extend the time to pay?
No. It extends the time to file. Tax due is still payable by the original due date.
When are Schedule K-1s due?
By the due date of the entity return, including a valid extension.
What if we already missed March 16 and did not file Form 7004?
The return is late. File it as soon as the books support a complete return. Review the late-filing penalty rules and the CP162A post. A tax professional can advise on relief.