A 3-shareholder S-Corp filed two months late. The IRS penalty? $1,320. Not for owing taxes. Just for filing late. The return showed zero tax due.
S-Corp deadlines are earlier than you think, and the penalties stack fast. Unlike your personal return due April 15, S-Corp returns are due March 15. Miss that deadline without an extension, and you’re looking at $220 per shareholder per month in penalties.
This guide covers every S-Corp deadline you need to know, how to get extensions, and what happens if you miss the mark.
Key Takeaways
- S-Corp tax returns (Form 1120-S) are due the 15th day of the 3rd month after fiscal year end
- Calendar year S-Corps: March 15 filing deadline
- 6-month automatic extension available via Form 7004 (extends to September 15)
- S-Corps are pass-through entities: the return is informational, shareholders report income on personal returns
- K-1s must be issued to shareholders by the filing deadline (March 15 or extended date)
- Late filing penalty: $220 per shareholder per month (2025/2026 rate)
- Extension extends filing deadline but NOT estimated tax payment requirements
- First-time penalty abatement available for qualifying taxpayers
Table of Contents
S-Corp Tax Return Due Date
The Form 1120-S deadline catches many business owners off guard. It’s a full month before personal returns are due.
The Core Rule
Form 1120-S is due on the 15th day of the 3rd month after your tax year ends.
For calendar year S-Corps (the vast majority), that means March 15.
If you have a fiscal year end, count three months forward. June 30 fiscal year end? Your return is due September 15.
Calendar Year Deadlines
| Tax Year | Filing Deadline | Extended Deadline |
|---|---|---|
| 2025 | March 16, 2026* | September 15, 2026 |
| 2026 | March 15, 2027 | September 15, 2027 |
| 2027 | March 16, 2028* | September 15, 2028 |
*March 15 falls on Sunday, deadline moves to Monday
Weekend and Holiday Adjustments
When March 15 falls on a weekend or federal holiday, the deadline shifts to the next business day. This happens more often than you’d think.
For 2026, March 15 falls on Sunday, so the deadline is Monday, March 16, 2026.
Always check the IRS calendar for your specific filing year. The IRS publishes official deadline dates each year that account for these adjustments.
What Gets Filed
On or before the deadline, you must submit:
- Form 1120-S: U.S. Income Tax Return for an S Corporation
- Schedule K-1: One for each shareholder, reporting their share of income, deductions, and credits
- All required schedules: Balance sheets, cost of goods sold, depreciation schedules, and other attachments as applicable
For more context on S-Corp taxation, see our Complete S-Corporation Tax Guide.
S-Corp Extension Options
If you can’t file by March 15, you have options. The extension process is straightforward.
Form 7004 Automatic Extension
File Form 7004 by the original deadline to get an automatic 6-month extension. No explanation required. No approval needed. If you file it correctly by March 15, you automatically have until September 15.
Key points about Form 7004:
- Automatic: The IRS grants the extension if you file the form properly
- No explanation needed: Just submit the form
- Electronic or paper: E-file is faster and provides immediate confirmation
- No payment typically required: S-Corps are pass-through entities and generally don’t owe corporate-level tax
How to File Form 7004
- Complete Form 7004 with your S-Corp information
- Select the correct form type (1120-S)
- File electronically through tax software or a tax professional
- Keep confirmation of filing for your records
Most tax software handles this automatically. If you’re working with a CPA, they file it as part of their standard process.
What the Extension Does
Filing Form 7004:
- Extends your Form 1120-S filing deadline to September 15
- Extends the K-1 issuance deadline to shareholders
- Gives you six additional months to gather information and prepare returns
What the Extension Does NOT Do
The extension has limits:
- Does not extend shareholder estimated tax payments: Shareholders still owe quarterly estimates on their usual schedule
- Does not extend state filing deadlines: Many states require separate extension filings
- Does not give more time for S-Corp election: Form 2553 deadlines are separate
- Does not extend any corporate-level tax payments: If your S-Corp owes built-in gains tax or other corporate taxes, those are still due by the original deadline
Extension Best Practices
File an extension even if you plan to file on time. Unexpected delays happen. Having the extension filed provides a safety net.
Keep your confirmation. Whether you e-file or mail, save proof that you submitted the extension by the deadline.
Mark the extended deadline on your calendar. September 15 will sneak up on you during summer.
Common Extension Mistakes
Assuming the extension is automatic without filing. The extension is automatic once you file Form 7004. If you don’t file the form, there’s no extension.
Missing the March 15 deadline to file the extension. You must file Form 7004 by the original deadline. A late extension request doesn’t help.
Forgetting state extensions. Federal extension doesn’t cover state returns. File state extensions separately.
Form 1120-S Preparation Services
S-Corp Estimated Tax Considerations
Here’s where S-Corp taxation gets confusing. Understanding who owes what and when is critical.
S-Corps Generally Don’t Pay Estimated Taxes
S-Corps are pass-through entities. The corporation itself usually doesn’t owe federal income tax. Income passes through to shareholders, who pay tax on their personal returns.
This means the S-Corp typically doesn’t make quarterly estimated tax payments. The responsibility falls on shareholders.
Exception situations where S-Corps do owe corporate-level tax:
| Situation | Tax Applies |
|---|---|
| Built-in gains (converted from C-Corp) | Yes |
| LIFO recapture | Yes |
| Excess passive investment income (with C-Corp E&P) | Yes |
| General operations | No |
If your S-Corp converted from C-Corp status, you may have built-in gains exposure. Consult with your tax professional about these situations.
Shareholder Estimated Taxes (Critical)
While the S-Corp may not owe quarterly estimates, shareholders absolutely do.
Shareholders must pay quarterly estimated taxes based on their share of S-Corp income (reported on K-1), plus any other income sources.
Quarterly estimated tax due dates:
- Q1: April 15
- Q2: June 15
- Q3: September 15
- Q4: January 15 (of the following year)
The timing creates planning challenges:
- S-Corp return due March 15
- Q1 shareholder estimated payment due April 15
- Getting K-1 early helps shareholders calculate their first quarterly payment
This is why timely S-Corp filings matter. Shareholders need their K-1 information to properly estimate their personal tax liability.
S-Corp Distributions Tax Rules
K-1 Issuance Requirements
Schedule K-1 is how S-Corp income gets reported to shareholders. Understanding K-1 requirements is essential for compliance.
What is a K-1?
Schedule K-1 (Form 1120-S) reports each shareholder’s share of:
- Ordinary business income or loss
- Rental income
- Interest, dividends, and royalties
- Capital gains and losses
- Section 179 deductions
- Charitable contributions
- Credits
- And other items
Shareholders use their K-1 to complete their personal tax returns. Without it, they can’t accurately report their S-Corp income.
K-1 Deadline
K-1s are due by the same deadline as Form 1120-S:
- March 15 for calendar year S-Corps
- September 15 if extended
You must both provide K-1s to shareholders AND file them with the IRS as part of the Form 1120-S package.
Electronic Delivery Options
K-1s can be delivered electronically if shareholders consent in advance. Electronic delivery must meet IRS requirements:
- Shareholder must affirmatively consent
- K-1 must be available by the deadline
- Shareholder can request paper copy at any time
Many accounting software platforms handle electronic K-1 delivery automatically.
What If K-1 Is Late?
Late K-1s create problems for shareholders:
- Personal return delays: Shareholders may need to file their own extensions
- Estimation required: Shareholders might estimate K-1 amounts and file, then amend later
- Planning difficulties: Hard to manage cash flow and estimated payments without knowing K-1 income
Pro Tip: Get your S-Corp return done early so shareholders can plan their personal returns. This is especially important in multi-shareholder S-Corps where delays affect multiple people.
S-Corp Late Filing Penalties
The penalties for late S-Corp returns are significant. They’re calculated per shareholder, per month late.
The Per-Shareholder Penalty
For 2025 and 2026, the penalty is $220 per shareholder per month (or partial month) the return is late, up to 12 months.
| Factor | Amount |
|---|---|
| Penalty per shareholder | $220/month |
| Maximum months | 12 |
| Calculation | Shareholders x Months Late x $220 |
Penalty Examples
Example 1: Single Owner S-Corp
You’re the sole shareholder. You file three months late.
Penalty: 1 shareholder x 3 months x $220 = $660
Example 2: Business Partners
Five shareholders. Two months late.
Penalty: 5 shareholders x 2 months x $220 = $2,200
Example 3: Family S-Corp
Three shareholders (you, spouse, adult child). Six months late.
Penalty: 3 shareholders x 6 months x $220 = $3,960
The penalties add up quickly with multiple shareholders. A family business with three shareholders and a full year’s delay could face $7,920 in penalties.
Interest on Unpaid Taxes
If your S-Corp owes tax at the corporate level (built-in gains, excess passive income), interest accrues on unpaid amounts. The current IRS interest rate hovers around 8% annually, adjusted quarterly.
First-Time Penalty Abatement
The IRS offers first-time penalty abatement (FTA) for taxpayers with clean compliance history.
To qualify:
- No penalties in the prior three tax years
- All required returns filed (or extensions filed)
- All tax due has been paid
How to request:
- Call the IRS directly and request FTA
- Or submit a written request
First-time abatement is often granted. It’s worth requesting if you qualify.
Reasonable Cause Relief
Beyond first-time abatement, the IRS may waive penalties for reasonable cause:
- Natural disasters affecting your ability to file
- Serious illness of the taxpayer or immediate family
- Death in the family
- Accountant’s error (with documentation)
- Fire, casualty, or other disaster destroying records
Reasonable cause requires a written explanation with supporting documentation.
How to Request Relief:
- File the late return
- Pay any tax due (if applicable)
- Submit penalty abatement request via letter or Form 843
- Include detailed explanation and documentation
- Wait for IRS response
First-Year S-Corp Filing Considerations
New S-Corps have unique timing considerations.
Short Tax Year Rules
Your first tax year as an S-Corp may be less than 12 months. This happens when:
- You form a new business mid-year
- An existing business elects S-Corp status effective mid-year
The return is still due on the 15th of the 3rd month after year end.
Example: S-Corp election effective July 1, calendar year end December 31. First return covers July 1 – December 31 (6 months). Return due March 15 of the following year.
Initial S-Corp Election Timing
Form 2553 (S-Corp election) has its own deadline: 2 months and 15 days from the effective date.
For existing businesses wanting current-year election, that deadline is March 15.
Don’t confuse Form 2553 (S-Corp election) with Form 1120-S (annual return). They serve different purposes and have different deadlines.
First-Year Payroll Setup
If you work in your S-Corp, you must have payroll running before year end. At minimum, issue yourself at least one W-2.
Don’t wait until December to set up payroll. Start early to ensure compliance. See our S-Corp Reasonable Compensation Guide for determining the right salary level.
First-Year K-1 Timing
Even one day of S-Corp status requires issuing K-1s. Shareholders report their pro-rata share of income or loss for the S-Corp period.
State S-Corp Filing Deadlines
Federal compliance is only part of the picture. Most states have their own requirements.
Not All States Follow Federal
While many states piggyback on federal S-Corp elections and deadlines, some have their own rules.
States with different requirements:
| State | Notes |
|---|---|
| California | $800 minimum franchise tax due April 15; requires annual LLC fee based on income |
| New York | Requires separate state S-Corp election (Form CT-6) |
| New Jersey | Requires separate CBT-2553 for state S election |
| Texas | Franchise tax (margin tax) applies; not income tax |
| Pennsylvania | Optional state S election affects tax treatment |
Check Your State
Before assuming you’re compliant, verify:
- State filing deadline: Same as federal or different?
- State extension requirements: Does federal extension cover state?
- State S-Corp election: Required separately or automatic?
- State-specific penalties: What happens if you’re late?
Pro Tip: Don’t assume federal extension covers state. File state extensions separately to avoid surprises.
S-Corp Tax Calendar at a Glance
Keep this calendar handy for S-Corp compliance:
| Date | Action Required |
|---|---|
| January 15 | Q4 estimated taxes due (shareholders) |
| January 31 | W-2s due to employees (see year-end payroll checklist) |
| January 31 | 1099s due to recipients (if applicable) |
| March 15 | Form 1120-S due (or file extension) |
| March 15 | K-1s due to shareholders |
| April 15 | Q1 estimated taxes due (shareholders) |
| April 15 | California $800 franchise tax due |
| June 15 | Q2 estimated taxes due (shareholders) |
| September 15 | Extended Form 1120-S due |
| September 15 | Extended K-1s due to shareholders |
| September 15 | Q3 estimated taxes due (shareholders) |
Frequently Asked Questions
When is my S-Corp tax return due?
Calendar year S-Corps: March 15. Fiscal year S-Corps: 15th day of the 3rd month after year end. File Form 7004 by the deadline for an automatic 6-month extension.
Can I get an extension for my S-Corp taxes?
Yes. File Form 7004 by March 15 for an automatic 6-month extension (to September 15). No explanation needed. The extension is automatic if properly filed.
What is the penalty for filing my S-Corp return late?
$220 per shareholder per month late, up to 12 months. A 3-shareholder S-Corp filed 2 months late = $1,320 penalty. First-time penalty abatement may be available.
When are S-Corp K-1s due?
Same deadline as Form 1120-S: March 15 (or September 15 with extension). K-1s must be provided to shareholders by this deadline so they can file personal returns.
Does an S-Corp pay estimated taxes?
Generally no. S-Corps are pass-through entities. However, shareholders must pay quarterly estimated taxes on their K-1 income. The S-Corp may owe tax if it has built-in gains from C-Corp conversion.
What if my S-Corp has a fiscal year end?
The deadline is the 15th day of the 3rd month after your fiscal year ends. Example: June 30 year end = September 15 deadline.
Does the extension extend my K-1 deadline?
Yes. If you extend Form 1120-S to September 15, K-1s are also due September 15. However, shareholders may need to extend their personal returns if waiting for K-1s.
Can I get penalty relief for late filing?
Yes. First-time penalty abatement is available if you have a clean 3-year compliance history. Reasonable cause relief may apply for circumstances beyond your control (illness, disaster, etc.).
Next Steps
Stay Compliant:
- Mark your calendar: March 15 and September 15 are the dates that matter
- File extension early: Even if you plan to file on time, file Form 7004 as a safety net
- Communicate with shareholders: They need K-1s for their personal returns
- Plan for state requirements: Check your state’s rules and file state extensions if needed
S-Corp penalties stack fast. $220 per shareholder per month adds up quickly, especially for multi-shareholder businesses. The penalties apply even when the S-Corp owes no tax.
If you’re managing S-Corp compliance on your own and want to ensure deadlines don’t slip, or if you’ve already missed a deadline and need help navigating penalty abatement, professional guidance can save you significant money and stress.