Tax

S-corp due dates 2026: filing deadlines, extensions, and penalties

July 19, 2026

S-corporations must file Form 1120-S by March 17, 2026 for the 2025 tax year (March 15 falls on a Sunday), and distribute Schedule K-1s to shareholders by the same deadline. Miss that date without filing an extension, and the IRS charges $240 per month per shareholder—even if you owe no tax.

This guide consolidates every S-corp deadline you must track in 2026: federal returns, quarterly payroll taxes, state franchise filings, extension rules, and the penalty math when things go wrong.

When Are S-Corp Taxes Due in 2026?

Form 1120-S is due March 17, 2026 for calendar-year filers. Fiscal-year S-corps file by the 15th day of the third month after their tax year ends.

Form 1120-S reports your S-corp's income, deductions, credits, and shareholder distributions. The return typically shows zero tax liability because S-corps are pass-through entities—profits and losses flow to shareholders' personal returns. You still must file to report that pass-through activity.

Schedule K-1 must be furnished to each shareholder by March 17, 2026. Each K-1 shows a shareholder's portion of income, deductions, and credits, which they report on their individual Form 1040 (due April 15, 2026). Late K-1s delay shareholder filings and trigger downstream penalties on their personal returns.

First-year S-corps: If you filed Form 2553 (S-corp election) by March 15, 2025, your first Form 1120-S is due March 15, 2026 for the 2025 tax year.

S-Corp Extension Deadline: September 15, 2026

File Form 7004 by March 15, 2026 to automatically extend your S-corp filing deadline to September 15, 2026. The extension is automatic; the IRS doesn't send approval notices. File electronically through tax software or mail a paper Form 7004 before the original March 15 deadline.

The extension applies to filing only—any tax owed is still due March 15 to avoid interest and penalties. S-corps rarely owe entity-level tax, but if you're subject to built-in gains tax or excess passive income tax, pay the estimated liability by March 15 even if you extend the return.

Shareholder K-1 deadline extends to September 15 when you file Form 7004, giving shareholders more time before they must file or amend their individual returns.

State extensions often piggyback federal Form 7004. California and New York automatically extend S-corp returns to September 15 when you file federal Form 7004, but verify your state's rules—some require a separate state extension form.

When Are Quarterly Payroll Taxes Due?

S-corps with employees must file Form 941 and deposit payroll taxes quarterly: April 30, July 31, October 31, 2026, and January 31, 2027. These deadlines apply to all S-corps that pay W-2 wages, including owner-employees.

Q1 2026 (January–March): due April 30, 2026
Q2 2026 (April–June): due July 31, 2026
Q3 2026 (July–September): due October 31, 2026
Q4 2026 (October–December): due January 31, 2027

Payroll tax deposits (federal income tax withholding, Social Security, Medicare) are due semi-weekly or monthly via EFTPS, separate from the quarterly Form 941 filing. Your deposit schedule depends on your total tax liability in a prior lookback period. Most small S-corps are monthly depositors (15th of the following month).

Owner-employee W-2 wages are reported on Form 941. The IRS scrutinizes S-corp shareholder-employees for reasonable compensation—you must pay yourself a market-rate salary for services performed before taking distributions. Underreporting W-2 wages to avoid payroll taxes is a common audit trigger.

S-Corp Estimated Tax Payment Deadlines

S-corps subject to built-in gains tax or excess passive income tax must make estimated payments on April 15, June 16, September 15, 2026, and January 15, 2027. Most S-corps pay no entity-level tax and skip this step entirely.

S-corps are pass-through entities, so income flows to shareholders who pay tax on their individual returns. The S-corp itself owes tax only in two situations:

Built-in gains tax: If you converted from a C-corp to an S-corp within the past five years and sell appreciated assets, you may owe tax on the built-in gain at the entity level.
Excess passive income tax: If more than 25% of your gross receipts are passive income (rents, royalties, dividends, interest) and you have accumulated earnings and profits from C-corp years, you owe tax on the excess.

Shareholders pay estimated taxes on their pass-through S-corp income via individual Form 1040-ES, using the same quarterly deadlines.

State S-Corp Tax Filing Deadlines (Top 5 States)

State S-corp returns generally follow the federal March 15 deadline, but franchise taxes, annual reports, and extension rules vary by state.

California:

Form 100S (S-corp return) due March 15, 2026
$800 minimum franchise tax due April 15, 2026
Extension to September 15, 2026 via Form FTB 3539 or automatic with federal Form 7004
First-year S-corps pay the $800 tax in their second year of business

New York:

Form CT-3-S due March 15, 2026
Extension to September 15, 2026 via Form CT-5.4
Fixed dollar minimum tax ($25 to $200,000+) based on New York receipts
Metropolitan Commuter Transportation Mobility Tax (MCTMT) may apply if you have payroll in the MTA region

Texas:

No state income tax, but franchise tax (Form 05-158) due May 15, 2026 for calendar-year filers
Franchise tax applies to S-corps with more than $1,230,000 in annualized total revenue
Annual report due May 15, 2026 (filed with Secretary of State)

Florida:

No state income tax; no S-corp return required
Annual report due May 1, 2026 ($150 fee, filed with Division of Corporations)
Late annual reports incur $400 penalty and potential administrative dissolution

Illinois:

Form IL-1120-ST due March 15, 2026
1.5% replacement tax on net income
Extension to September 15, 2026 via Form IL-505-I
$800 minimum replacement tax for S-corps with gross receipts over $4 million

Check your state's Department of Revenue or Franchise Tax Board website for exact deadlines. Some states have different due dates or no S-corp return requirement.

What Is the Penalty for Filing S-Corp Taxes Late?

The IRS charges $240 per month (or part of a month) per shareholder for late S-corp returns, up to 12 months. The penalty applies even if you owe no tax, because the IRS requires Form 1120-S to report pass-through income to shareholders.

The failure-to-file penalty is $240 per shareholder per month for returns due in 2026 (inflation-adjusted from $235 in 2024-2025). The penalty starts the day after the deadline:

No extension filed: penalty starts March 18, 2026
Extension filed: penalty starts September 16, 2026

Maximum penalty: 12 months, or $2,880 per shareholder for a full year late.

Example: A 3-shareholder S-corp files on May 1, 2026 (1.5 months late, no extension). The penalty is $240 × 2 months × 3 shareholders = $1,440. Partial months count as full months—filing 1 day late or 30 days late in a given month costs the same.

Late payment penalty (if entity-level tax is owed): 0.5% per month on unpaid tax, plus interest (8% annually as of Q1 2026 for corporate underpayments).

Failure-to-furnish K-1 penalty: $320 per K-1 if you don't provide Schedule K-1s to shareholders by the deadline. This is separate from the $240/month/shareholder penalty for late 1120-S filing—you can owe both.

Can You Request an Extension for S-Corp After the Due Date?

The IRS waives late-filing penalties if you demonstrate reasonable cause and attach a signed statement explaining the delay. Reasonable cause means you exercised ordinary business care and prudence, but circumstances beyond your control prevented timely filing.

Accepted reasons:

Death or serious illness of the business owner or immediate family member
Fire, casualty, or natural disaster that destroyed business records
Reliance on erroneous written advice from the IRS
Tax preparer failure, if you provided all necessary records with adequate time to file

Not accepted:

"I forgot the deadline"
"I was too busy"
"I didn't know S-corps had to file"
"I couldn't afford to pay the tax" (payment issues don't excuse filing—you can file with zero payment)

How to request reasonable cause relief:

Attach a signed statement to your late Form 1120-S explaining the cause, relevant dates, and why you couldn't file on time despite exercising ordinary care.
File the return as soon as possible after the missed deadline. Delay weakens your reasonable cause argument.
Provide documentation if possible (death certificate, insurance claim, hospital records, correspondence with the failed preparer).

The IRS reviews reasonable cause requests case-by-case. If denied, you can appeal via Form 843 (Claim for Refund and Request for Abatement).

What to Do If You Missed the S-Corp Filing Deadline

File your late 1120-S immediately, pay any tax owed, and attach a reasonable cause statement if applicable. The penalty clock is running.

Step 1: Prepare and e-file Form 1120-S as soon as possible. Every month (or partial month) late adds $240 per shareholder to your penalty.

Step 2: Distribute K-1s to shareholders immediately. Late K-1s delay shareholders' individual returns, potentially triggering penalties on their personal filings or requiring amended returns if they already filed.

Step 3: Pay any entity-level tax owed via EFTPS or IRS Direct Pay to stop interest accrual.

Step 4: Attach a reasonable cause statement if you have one. Proactive disclosure is more credible than reactive appeals.

Step 5: Expect a CP161 notice if you don't have reasonable cause. The IRS will mail a penalty assessment 4–8 weeks after you file. You can appeal via Form 843 if your circumstances change.

Shareholder impact: Late K-1s force shareholders to file extensions on their individual 1040s or amend already-filed returns. If a shareholder filed their 1040 in early April using estimated S-corp income and your actual K-1 shows different numbers, they must file Form 1040-X (amended return), which delays refunds and increases audit risk.

State filings: File late state S-corp returns separately. State penalties vary:

California: 5% of unpaid tax per month, up to 25% maximum
New York: 5% of unpaid tax per month, up to 25% maximum
Illinois: $250 or 2% of tax due (whichever is greater) per month, up to 12 months

Check your state's Department of Revenue for exact penalty calculations and reasonable cause procedures.

2026 S-Corp Tax Deadline Calendar (At-a-Glance)

Date	Filing/Payment	Form	Notes
Jan 31, 2026	Q4 2025 payroll tax return	Form 941	Report Oct–Dec 2025 wages and withholding
March 17, 2026	S-corp tax return + K-1s	Form 1120-S, Schedule K-1	Federal deadline (March 15 is Sunday); also CA Form 100S, NY CT-3-S, IL IL-1120-ST
March 17, 2026	Extension (if needed)	Form 7004	Extends deadline to Sept 15; file before original deadline
April 15, 2026	Q1 estimated tax (if applicable)	Form 1120-W	Only if S-corp owes built-in gains or excess passive income tax
April 15, 2026	CA franchise tax	$800 minimum	Due 15th day of 4th month (separate from Form 100S)
April 30, 2026	Q1 2026 payroll tax return	Form 941	Report Jan–Mar 2026 wages
May 1, 2026	FL annual report	—	$150 fee; filed with Division of Corporations
May 15, 2026	TX franchise tax + annual report	Form 05-158	Calendar-year filers; no income tax in TX
June 16, 2026	Q2 estimated tax (if applicable)	Form 1120-W	June 15 is Sunday
July 31, 2026	Q2 2026 payroll tax return	Form 941	Report Apr–Jun 2026 wages
Sept 15, 2026	Extended S-corp return deadline	Form 1120-S, Schedule K-1	If Form 7004 filed by March 15
Sept 15, 2026	Q3 estimated tax (if applicable)	Form 1120-W	—
Oct 31, 2026	Q3 2026 payroll tax return	Form 941	Report Jul–Sep 2026 wages
Jan 15, 2027	Q4 2026 estimated tax (if applicable)	Form 1120-W	—
Jan 31, 2027	Q4 2026 payroll tax return	Form 941	Report Oct–Dec 2026 wages

Weekend/holiday rule: If a deadline falls on a Saturday, Sunday, or federal holiday, the due date moves to the next business day.

State deadlines vary. Confirm franchise tax, annual report, and extension due dates with your state's Department of Revenue or Secretary of State.

Frequently Asked Questions About S-Corp Tax Deadlines

When is the first S-corp filing due after election?

If you filed Form 2553 (S-corp election) by March 15, 2025, your first Form 1120-S is due March 17, 2026 for the 2025 tax year.

Can you file an S-corp extension after the due date?

No. Form 7004 must be filed by the original March 15 deadline to extend your filing deadline to September 15. If you miss March 15 without filing an extension, you cannot retroactively extend. However, you can still request reasonable cause penalty relief when you file your late return if you have qualifying circumstances.

What happens if you file S-corp taxes late?

The IRS assesses a $240 per month per shareholder penalty for late Form 1120-S filing, even if you owe no tax. A 2-shareholder S-corp filing 3 months late owes $1,440 ($240 × 3 months × 2 shareholders). You'll also face a separate $320 per K-1 penalty if you don't provide Schedule K-1s to shareholders by the deadline.

Do S-corps pay quarterly estimated taxes?

Most S-corps pay no entity-level tax because income passes through to shareholders. Estimated payments are required only if your S-corp owes built-in gains tax or excess passive income tax. Shareholders pay estimated taxes on their pass-through S-corp income via individual Form 1040-ES quarterly.

What is the S-corp extension deadline for 2026?

File Form 7004 by March 15, 2026 to automatically extend your S-corp filing deadline to September 15, 2026. The extension applies to filing only; any tax owed is still due March 15.

Let Uplinq track every S-corp deadline, file your 1120-S, and distribute K-1s on time. Book a demo to automate compliance and eliminate penalty risk. Our platform syncs federal and state deadlines, calculates shareholder basis in real time, and alerts you before every filing date.

This article is for general informational purposes only and does not constitute tax, legal, or accounting advice. Tax rules and fees change frequently and vary by state and situation. Consult a qualified professional before making decisions about your business.