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S Corporation Tax Deadline 2026: Form 1120-S, Schedule K-1, Extension, and Shareholder Dates

A practical 2026 S corporation tax deadline guide covering the March 16 Form 1120-S and Schedule K-1 due date, Form 7004 extension, September 15 extended deadline, S election timing, entity-level estimated tax dates, payroll and 1099 deadlines, penalties, and official IRS Business Tax Account video guidance.

Published: May 7, 2026Updated: May 7, 2026

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S Corporation Tax Deadline 2026

The main S corporation tax deadline in 2026 was March 16, 2026 for calendar-year S corporations filing a 2025 Form 1120-S. March 15 fell on a Sunday, so the federal deadline moved to Monday, March 16.

This article is updated as of May 7, 2026. That means the original 2025 Form 1120-S deadline, shareholder Schedule K-1 deadline, and Form 7004 extension deadline have already passed for most calendar-year S corporations. If a valid extension was filed, the key federal date is now September 15, 2026.

Countdown Timer

The tracked 2026 IRS deadline sequence is complete.

Deadline Summary

March 16 was the original due date

Calendar-year S corporations had to file Form 1120-S, furnish shareholder K-1s, or file Form 7004 by March 16, 2026.

Extension Alert

September 15 requires Form 7004

The September deadline generally applies only when the S corporation requested a valid 6-month extension by the original due date.

Payment Alert

Extension is not payment relief

Form 7004 extends filing time. It does not extend time to pay any entity-level tax the S corporation owes.

S Corporation Action Buttons

Use calculators for planning. Use IRS systems and professional review for filing, extension, penalty, election, and payment decisions.

Check Owner Wages Check Payroll FICA IRS Form 1120-S IRS Form 7004

Important 2026 S Corporation Dates

S corporation deadlines sit between payroll, information returns, the entity return, shareholder K-1s, individual tax returns, and state pass-through rules. Treat the dates as one close calendar, not isolated forms.

2026 S Corporation Deadline Table

Date	Deadline	Applies To	Action
February 2, 2026	W-2 and 1099 operating deadline	S corporations with employees, owner-employees, contractors, or reportable vendors	This date has passed as of this May 7, 2026 update. Fix missed payroll or information returns before finalizing shareholder return packages.
March 16, 2026	Form 1120-S and Schedule K-1 due	Calendar-year S corporations reporting 2025 tax year activity	File Form 1120-S, furnish Schedule K-1 and any required Schedule K-3 to shareholders, or file Form 7004 by this date.
March 16, 2026	Form 7004 extension request due	Calendar-year S corporations needing more time to file the 2025 return	Request the automatic 6-month filing extension. Pay any entity-level tax due by the original due date.
March 16, 2026	Many 2026 S elections due	Eligible calendar-year entities electing S corporation treatment effective January 1, 2026	Form 2553 generally had to be filed no more than 2 months and 15 days after the beginning of the tax year.
April 15, 2026	First S corporation entity estimated-tax installment if applicable	S corporations expecting certain entity-level taxes	Entity-level tax is not the same as shareholder individual estimated tax. Review both workflows separately.
June 15, 2026	Second S corporation entity estimated-tax installment if applicable	Calendar-year S corporations with required entity-level estimated tax payments	Recalculate special entity-level taxes and pass-through information before midyear payments.
September 15, 2026	Extended Form 1120-S and K-1 deadline	Calendar-year S corporations with a valid Form 7004 extension	File the completed return, furnish shareholder schedules, and resolve K-2/K-3 and state pass-through items.
December 15, 2026	Fourth S corporation entity estimated-tax installment if applicable	Calendar-year S corporations that owe entity-level estimated tax	Use final-year projections to prevent underpayment exposure before year-end close.

Fiscal-year S corporations and short-year returns use different due-date math. Disaster relief, state legal holidays, state tax law, or entity-specific elections can also move deadlines.

Form 1120-S and Schedule K-1 Deadline

Form 1120-S reports the income, gains, losses, deductions, credits, and other items of a domestic corporation or eligible entity with a valid S corporation election. The return drives shareholder Schedule K-1 reporting, which shareholders use on their own returns.

Entity Return

Form 1120-S

The S corporation files the federal entity return. Even if no entity-level income tax is due, the return can still be required.

Shareholder Package

Schedule K-1 and possible K-3

Shareholders need K-1 data before filing individual returns. International items may require Schedule K-2 and K-3 analysis.

Extension Result

K-1 timing follows the extended return

If Form 7004 was validly filed, shareholder schedules are generally finalized by the extended September 15 deadline.

Correction Risk

A corrected K-1 can ripple outward

If a K-1 changes after shareholders file, amended individual and state returns may need to be evaluated.

S Corporation Extension Rules

Form 7004 is the normal federal extension mechanism for Form 1120-S. For calendar-year S corporations, a timely Form 7004 generally gives a 6-month filing extension from March 16 to September 15, 2026. The extension request had to be filed by the original due date.

Extension Form

Form 7004

Use Form 7004 to request an automatic extension of time to file Form 1120-S. Keep acceptance proof with the permanent tax file.

Not Payment Relief

Tax still due at original date

Any entity-level tax due should be paid by the original return deadline even when the return itself is extended.

Shareholder Impact

K-1s may be delayed

Shareholders often cannot finish accurate individual returns until final K-1s are available, so entity extension planning affects owner filing.

State Layer

State extension may differ

Some states accept a federal extension, some require state action, and many still require payment by the original state due date.

Payment Rules and Estimated Taxes

S corporations are pass-through entities, but that does not mean the entity never pays federal tax. Entity-level tax can arise from built-in gains, excess net passive income, investment credit recapture, LIFO recapture, or other special items. IRS Form 1120-S instructions say tax due is generally payable by the return due date, not the extended due date.

For calendar-year S corporations that owe entity-level estimated tax, the IRS 2025 Form 1120-S instructions list 2026 installments on April 15, June 15, September 15, and December 15. Shareholders separately evaluate individual estimated tax on wages, K-1 income, investment income, and other personal tax items.

S Corporation Election Deadline

The S election is separate from the annual Form 1120-S return. Form 2553 is used by an eligible corporation or entity electing S corporation treatment. IRS instructions generally say to file no more than 2 months and 15 days after the beginning of the tax year the election is to take effect, or during the preceding tax year.

For many calendar-year entities seeking S corporation treatment effective January 1, 2026, that timing points to March 16, 2026 after the Sunday deadline adjustment. Late election relief can exist, but it should be handled with tax professional review.

Late Filing and Penalty Risk

IRS Form 1120-S instructions warn that penalties can apply when a return is late or does not include required information. For returns with no tax due, the penalty can be based on each month or part month the return is late, multiplied by the number of shareholders. If tax is due, unpaid-tax penalties and interest can be added.

The same IRS instructions list separate penalties for failing to furnish Schedule K-1 or Schedule K-3 information timely or correctly. If the corporation receives a penalty notice, the instructions say to respond with an explanation rather than attaching a penalty explanation to the original return.

Payroll, W-2, and 1099 Deadlines

S corporation tax deadline planning is weak if payroll and information returns are not closed first. Owner-employees may need W-2 wages. Contractors and vendors may need Forms 1099. Payroll tax returns and deposits need to reconcile to wage deductions and officer compensation on the S corporation return.

W-2 Workflow

Owner-employee wages

Forms W-2 for 2025 wages were due to employees and SSA on February 2, 2026. W-2 payroll should reconcile before the Form 1120-S is filed.

1099 Workflow

Contractor and vendor reporting

Forms 1099-NEC for 2025 nonemployee compensation were also due February 2, 2026. Other 1099 filing dates may differ.

Payroll Returns

Forms 941 and 940

Employment tax filings, deposits, and wage records can affect deductions, officer pay, and state payroll compliance.

State and Local S Corporation Deadlines

State S corporation deadlines can be more complicated than the federal date. A state may require an S corporation return, franchise tax, annual report, pass-through entity tax election or payment, composite return, nonresident withholding, local business tax, or secretary-of-state filing.

Do not assume that federal Form 7004 extends every state filing. Some states follow the federal extension automatically, some require a separate state extension, and many separate filing relief from payment obligations.

S Corporation Deadline by Taxpayer Type

The March and September entity dates connect to different responsibilities for the entity, owner-employees, passive shareholders, LLC owners, and new S election filers.

S Corporation Workflow

Calendar-Year S Corporations

The core 2026 date was March 16 for Form 1120-S, shareholder K-1s, and Form 7004 extension requests. A valid extension generally moves the filing deadline to September 15, 2026.

S Corporation Workflow

Fiscal-Year S Corporations

Fiscal-year S corporations use the 15th day of the third month after the end of the tax year, adjusted for weekends and legal holidays. State deadlines can follow a different pattern.

S Corporation Workflow

LLCs Taxed as S Corporations

An LLC with a valid S election generally files Form 1120-S for federal income tax, but may still owe state LLC fees, annual reports, franchise taxes, or gross receipts taxes.

S Corporation Workflow

Owner-Employees

Owner-employees usually need W-2 payroll records and K-1 records. Wages, withholding, distributions, and basis are separate files that should be reconciled before shareholder returns are filed.

S Corporation Workflow

Passive Shareholders

Passive shareholders need final K-1 data to evaluate passive activity limitations, suspended losses, state sourcing, credits, and whether estimated payments were enough.

S Corporation Workflow

New S Elections

A new or converting entity should separate Form 2553 election timing from the Form 1120-S filing deadline. Late election relief can exist, but should not be treated as routine planning.

S Corporation Deadline Action Checklist

Use this checklist to clean up a missed March filing, finish an extended September filing, or build the next year-end close process.

Documents Needed

Final books, trial balance, profit and loss statement, balance sheet, bank reconciliations, and loan schedules.
Shareholder ownership records, stock basis and debt basis support, distributions, contributions, and shareholder loan records.
Payroll records, owner-employee W-2s, Forms 941, Form 940, payroll tax deposits, and officer compensation support.
1099 records, vendor W-9s, contractor payments, rent, interest, legal fees, and state information-return records.
Prior-year return, prior-year Schedule K-1s, depreciation schedules, fixed-asset records, state returns, and notices.

Filing Steps

Confirm the entity is actually an S corporation for the tax year, including election status and any termination issue.
Reconcile book income to tax income, owner payroll to payroll returns, and distributions to shareholder basis records.
Prepare Form 1120-S, Schedule K, Schedule K-1, and any required Schedule K-2 or K-3 items before shareholder return work begins.
File Form 7004 by the original due date if more time is needed, and pay entity-level tax that may be due.
Deliver shareholder K-1 packages and keep proof of electronic or physical delivery.

Mistakes to Avoid

Treating September 15 as available without a timely Form 7004 extension.
Assuming an S corporation never owes entity-level federal tax.
Issuing K-1s before payroll, W-2, 1099, depreciation, and shareholder basis records are reconciled.
Ignoring state pass-through entity tax, franchise tax, composite return, or nonresident withholding requirements.
Mixing owner wages and shareholder distributions without payroll and reasonable-compensation review.

Shareholder Checklist

Wait for a final Schedule K-1 before filing a shareholder individual return unless a professional advises otherwise.
Track basis, suspended losses, distributions, loans, guarantees, and prior-year carryovers outside the K-1 alone.
Compare K-1 income with shareholder estimated payments and W-2 withholding before the individual deadline.
Review whether K-1 information affects QBI, passive activity limits, net investment income tax, credits, or state returns.
If a corrected K-1 arrives after filing, evaluate whether an amended return is needed.

Calculator Tools for S Corporation Planning

CalculatorWallah tools do not prepare Form 1120-S, Schedule K-1, Form 7004, or Form 2553. Use official IRS systems and tax software for filing. Use calculators to review payroll, shareholder withholding, FICA, estimated-tax pressure, and individual tax impact.

Owner Payroll

Check wages and withholding

Use the Paycheck Calculator when reviewing owner-employee wages, pre-tax deductions, and federal withholding before W-2 and K-1 planning.

Payroll Tax

Separate FICA from pass-through income

Use the FICA Tax Calculator to separate Social Security and Medicare tax on wages from shareholder K-1 income.

Shareholder Return

Estimate individual tax impact

Use the Federal Income Tax Calculator after K-1 income, W-2 wages, deductions, credits, and estimated payments are known.

Mixed Income

Compare S corp, W-2, and 1099 flows

Use the Self-Employment Tax Calculator carefully when comparing contractor income, Schedule C profit, and S corporation wage/distribution structures.

Official IRS Video

I found an official IRS Business Tax Account video that is relevant to S corporation tax account access. I did not find a current official IRS video dedicated only to the 2026 S corporation filing deadline, so the dates in this article are based on written IRS instructions and Publication 509.

IRS: Business Tax Account Overview

This IRS video is useful for understanding Business Tax Account access for eligible entities and authorized users. Written IRS instructions should control filing-date and extension decisions.

S Corporation Deadline Questions

The FAQ schema for this page covers the core S corporation deadline issues: March 16 filing, Schedule K-1, Form 7004, September 15 extension, Form 2553 election timing, estimated taxes, shareholder return timing, penalties, LLCs taxed as S corporations, and state deadline differences.

Schema, Trust, and Updates

This page is maintained as a business tax deadline guide, not individualized tax, legal, payroll, accounting, or entity-formation advice. It is marked in the tax article cluster, uses FAQ schema, includes VideoObject schema for the official IRS Business Tax Account video, and cites IRS Form 1120-S, Publication 509, Form 7004, Form 2553, Business Tax Account, e-file, and payroll sources.

Last updated: May 7, 2026. Deadline-sensitive S corporation facts should be checked against current IRS instructions, state revenue agency rules, secretary-of-state requirements, payroll provider records, and qualified tax professional review before filing, paying, extending, or responding to penalties.

Frequently Asked Questions

For calendar-year S corporations filing a 2025 Form 1120-S, the federal due date was Monday, March 16, 2026 because March 15, 2026 fell on a Sunday. The same date applied to furnishing Schedule K-1 to shareholders unless an extension was properly filed.

A calendar-year S corporation generally had to file its 2025 Form 1120-S by March 16, 2026. Fiscal-year and short-year S corporations use the 15th day of the third month after the end of the tax year, adjusted for weekends and legal holidays.

For a calendar-year S corporation, Schedule K-1 and, if applicable, Schedule K-3 generally had to be provided to shareholders by March 16, 2026, unless the corporation obtained a valid extension.

For a calendar-year S corporation that filed Form 7004 by March 16, 2026, the extended Form 1120-S deadline is September 15, 2026. The extension is for filing, not for paying entity-level tax that may be due.

No. Form 7004 generally extends the time to file the business return. It does not extend the time to pay tax. Any S corporation entity-level tax due should be paid by the original due date.

Most S corporation income passes through to shareholders, but S corporations can still owe certain entity-level federal taxes, such as built-in gains tax, excess net passive income tax, investment credit recapture, LIFO recapture, or other special taxes.

For a calendar-year S corporation that owes entity-level estimated tax, the 2026 installments are due April 15, June 15, September 15, and December 15, 2026. Shareholders have their own individual estimated-tax obligations.

For many calendar-year entities that wanted S corporation treatment effective January 1, 2026, Form 2553 was due no more than 2 months and 15 days after the beginning of the tax year, which points to March 16, 2026 after the Sunday adjustment.

IRS instructions allow penalties when Form 1120-S is late or missing required information. For returns with no tax due, the penalty can be monthly and shareholder-based; if tax is due, unpaid-tax penalties and interest can also apply.

The S corporation return and K-1 workflow is due in March for calendar-year entities. Individual shareholder Form 1040 returns generally follow the individual deadline, such as April 15, 2026 for many 2025 individual returns unless extended.

Not always. States can have separate S corporation returns, franchise taxes, pass-through entity taxes, composite returns, nonresident withholding, annual reports, and extension rules.

If an LLC has a valid S corporation election and files Form 1120-S, the federal S corporation return deadline generally applies. The legal entity may still have state LLC annual fees, franchise taxes, or secretary-of-state filings with different due dates.