S Corp and LLC Filing Deadlines

These dates come from the Form 1120-S , Form 1065 , and Form 1120 instructions, along with section 6072 and the Form 7004 instructions . This page covers entity returns only. For the full calendar, including quarterly estimated tax dates, use our tax due date calendar. The S election has its own deadline, and that is on our Form 2553 page.

State returns run on their own rules. A state deadline, franchise tax, or annual LLC fee can come due on a different date from anything in this table, so check each state where the business is registered or files.

Form 1120-S is the form for S corporations. Form 1120 is the form for C corporations. People searching for "Form 1120 S corp" usually mean Form 1120-S, and the difference matters.

An S corporation files Form 1120-S if it elected S status on Form 2553, the IRS accepted the election, and the election remains in effect. Income generally passes through to shareholders on Schedule K-1. The return is due the 15th day of the 3rd month after the tax year ends.

A C corporation files Form 1120 and generally pays its own income tax. The return is due the 15th day of the 4th month after the tax year ends. The Form 1120 instructions list S corporations among the entities that use a different return.

Do not file Form 1120-S for any tax year before the election takes effect. The IRS says so directly in the instructions . If you are not sure whether the IRS accepted your election, look for your CP261 notice. The instructions say to call 800-829-4933 if you have heard nothing within 2 months of filing Form 2553, or 5 months if you checked box Q1.

Still deciding on the election itself? Start with what an S corp is and run the numbers in our S corp tax calculator.

An LLC is a state-law entity. For federal tax, the IRS treats it as a partnership, a corporation, or part of the owner's return. So "the LLC tax deadline" is really four possible deadlines:

• Two or more members, no election: partnership. Form 1065 by March 15, 2027. The return is required unless the LLC neither received income nor had expenses that would be deductions or credits. Our Form 1065 guide covers the return itself.
• One member, no election: disregarded. The IRS reports a business owned by an individual on Schedule C, a rental generally on Schedule E, and a farm on Schedule F. All of it goes on the Form 1040 due April 15, 2027. There is no separate federal income tax return for the LLC.
• S election on Form 2553: Form 1120-S by March 15, 2027, once the election is in effect.
• Corporate election on Form 8832, no S election: Form 1120 by April 15, 2027.

A disregarded LLC is still treated as a separate entity for employment taxes and certain excise taxes. Payroll returns have their own dates even when the income tax return is the owner's Form 1040.

Not sure which one you are? Look at the last return you filed. An IRS acceptance letter for Form 8832 or a CP261 notice also answers it. If you never filed either election, the defaults above generally apply.

Form 7004 is the automatic extension for business returns, including Forms 1120-S, 1065, and 1120. The extension is generally 6 months. It has to be filed on or before the return's due date, so March 15, 2027 for Forms 1120-S and 1065, and April 15, 2027 for Form 1120.

Form 4868 is the automatic extension for your individual return. The IRS gives up to 6 more months if you request it by the due date, which takes a calendar-year return to October 15, 2027. Making an electronic payment and marking it as an extension also works, and that IRS page lists the ways to do it.

A single-member LLC owner needs only Form 4868, because the business is on the Form 1040. An S corporation owner or LLC partner who needs more time on both returns files both forms. Form 7004 for the business does nothing for your personal return, and the reverse is also true.

The Form 7004 instructions are plain about it: the form does not extend the time to pay any tax due. Interest runs from the regular due date, even with an extension. The late payment penalty is generally 0.5% of the unpaid tax for each month or part of a month, up to 25%.

• S corporation: It usually owes no federal income tax itself, but some taxes can apply at the company level, such as the tax on built-in gains and the excess net passive income tax. Any such tax is due in full by the return's due date. Income that passes through to you is paid on your Form 1040.
• Partnership LLC: Partners generally pay on their own returns. March 15 is a filing date for the LLC, and April 15 is the payment date for the people.
• Single-member LLC: Filing and payment both run through your Form 1040, due April 15, 2027.
• C corporation: It pays its own tax, due by April 15, 2027 for calendar 2026, even if Form 7004 moves the return to October 15.

Owners also generally make quarterly estimated payments during the year if they expect to owe at least $1,000. Those dates live on our due date calendar, and our estimated tax guide covers the method.

Quick example. A single-member LLC owner files Form 4868 on time, pays nothing toward a $10,000 balance by April 15, 2027, then files and pays on October 15, 2027. The return is on time. The late payment penalty is generally 6 months x 0.5% x $10,000 = $300, plus interest. Some taxpayers who paid enough by April 15 may qualify for relief, but do not assume it.

A K-1 is due to each owner by the same date the entity's return is required to be filed. The Form 1120-S instructions and the Form 1065 instructions use nearly the same words, and both cover anyone who was an owner at any time during the year. That includes an owner who sold out in February. See section 6037(b) for S corporations and Regulations section 1.6031(b)-1T for partnerships. The partnership regulation expressly determines the date with regard to extensions.

For calendar 2026 that means March 15, 2027, or September 15, 2027 with a valid Form 7004. The awkward part is the gap. An owner's Form 1040 is due April 15, so a K-1 that arrives in September means the owner needs Form 4868 and an estimated payment. Tell your owners early if you plan to extend.

For what the form reports, read our Schedule K-1 guide and the 1120-S vs 1065 K-1 comparison.

Under section 6072 , the fiscal year version of each deadline uses the same month count: the 15th day of the 3rd month after year end for S corporations and partnerships, and the 15th day of the 4th month for C corporations.

Example. With a tax year ending September 30, 2027, an S corporation's Form 1120-S is due December 15, 2027. A C corporation's Form 1120 would land on January 15, 2028, a Saturday. Monday, January 17 is Martin Luther King Jr. Day, so that due date moves to Tuesday, January 18, 2028.

Most S corporations and partnerships cannot just pick a fiscal year. Section 1378 allows an S corporation a year ending December 31 or another period with an established business purpose. A section 444 election on Form 8716 is also possible, with limits and required payments . Partnerships generally must follow the tax year rules based on their partners, as explained in Publication 538 .

C corporations with a June 30 year end were a special case. The 3rd-month rule in the regulations applies to tax years beginning before January 1, 2026, and the Form 7004 instructions give those earlier years a 7-month extension and tax years beginning in 2026 a 6-month extension. A June 30, 2027 year end, which begins in 2026, follows the regular 4th-month rule, so the return is due October 15, 2027.

When a due date falls on a Saturday, Sunday, or legal holiday, section 7503 treats the next regular day as on time. For tax year 2026, none of the main dates need it: March 15, 2027 is a Monday, April 15 is a Thursday, September 15 is a Wednesday, and October 15 is a Friday.

Do not reuse last year's dates. March 15, 2026 was a Sunday, so the IRS moved calendar-year 2025 returns to March 16, 2026. That date does not carry forward.

The 2027 amounts are in Rev. Proc. 2025-32 . The Form 1120-S and Form 1065 penalties are the ones that surprise people, because they have nothing to do with tax owed. They count owners. Anyone who was a shareholder or partner during any part of the year counts, and at the 12-month cap that comes to $3,120 per owner.

Worked example: a three-owner S corporation

A hypothetical calendar-year S corporation has three shareholders and owes no entity-level tax. It does not file Form 7004. Its 2026 Form 1120-S goes in on June 2, 2027. Counting from March 15, that is three months or parts of months late.

A Form 7004 filed on time, followed by a return and K-1s by September 15, would have prevented all of it. And if that company had extended, then filed on September 16, one day late would still count as one month: 3 x $260 = $780.

A Schedule C owner example. A single-member LLC owner has a $10,000 unpaid balance, files no extension, and files and pays on July 1, 2027. That is three months or parts of months. The failure to file penalty is 4.5% a month after the late payment offset, or $1,350. The late payment penalty is 0.5% a month, or $150. Together that is $1,500, plus interest. The IRS explains the offset here .

Can the penalty be removed?

Possibly. The Form 1120-S and Form 1065 instructions both allow relief for reasonable cause. The instructions say to wait for the IRS notice and respond with an explanation, not to attach one to the return.

The IRS also has administrative relief for a clean record. Its relief page says First Time Abate is moving to a new Automatic Exemption from Penalty starting with 2025 tax year returns. Both generally look for the same return type filed on time for the prior three years. The page lists the S corporation failure to file penalty as eligible for relief, though its list of return series for the automatic version names Forms 1040, 1065, and 1120 without spelling out Form 1120-S. A newer business may not have the three-year history at all, so treat any of this as a fallback, not a plan.

Publication 538 says an entity not in existence for the entire year still files for the time it existed. Its example: a corporation organized July 1 with a calendar year files a first return covering July 1 through December 31.

• New S corporation, starting August 10, 2026 with a valid election: a short-period Form 1120-S covering August 10 through December 31, 2026, due March 15, 2027.
• New C corporation, same start: a short-period Form 1120 due April 15, 2027. The instructions set it at the 15th day of the 4th month after the short period ends.
• New multi-member LLC, same start: a Form 1065 due March 15, 2027, unless it had no income and no expenses treated as deductions or credits.
• Existing LLC with an S election effective January 1, 2027: keep your current return for 2026. The first Form 1120-S covers 2027 and is due March 15, 2028.

The start date for a new S corporation is not always the state formation date. Form 2553 uses the earliest of when the entity first had shareholders, first had assets, or began doing business, as our Form 2553 page explains. Filing a short-year extension? Form 7004 line 5b asks for the reason for the short year.

Two other events create a short year. A dissolved corporation generally files by the 15th day of the 3rd month after dissolution on Form 1120-S, or the 4th month on Form 1120. And an S election that terminates mid-year and reverts to C status means a short Form 1120-S, due by the due date, including extensions, of the C corporation's short-year return.

If your election was missed altogether, read our late S corp election guide before you file anything for the year. If the first-year books are not ready, our bookkeeping guide for S corps shows what the return needs.