I see this about twice a month: a business owner thinks filing an extension bought them time to pay. It didn’t. The extension gave them six more months to file paperwork. The IRS still wanted the money by March 16.
If you own an S-Corp, partnership, or LLC, you need to know exactly when your 2026 business tax extension deadlines fall and what happens if you miss them. This guide covers every entity type, the forms you’ll file, penalties you’ll face if you’re late, and how to get relief if you’ve already missed a deadline.
Key Takeaways:
- S-Corps and partnerships: File by March 16, 2026 or extend to September 15, 2026
- C-Corps: File by April 15, 2026 or extend to October 15, 2026
- Extensions give you more time to file, not more time to pay
- Late filing penalty: $245 per shareholder/partner per month (up to 12 months)
- First-time penalty abatement may eliminate penalties if you have a clean 3-year history
Table of Contents
2026 Business Tax Extension Deadlines at a Glance
Here’s your quick-reference table for every business entity type:
| Entity Type | Original Deadline | Extension Form | Extended Deadline |
|---|---|---|---|
| S-Corporation (Form 1120-S) | March 16, 2026 | Form 7004 | September 15, 2026 |
| Partnership (Form 1065) | March 16, 2026 | Form 7004 | September 15, 2026 |
| Multi-Member LLC | March 16, 2026 | Form 7004 | September 15, 2026 |
| C-Corporation (Form 1120) | April 15, 2026 | Form 7004 | October 15, 2026 |
| Single-Member LLC | April 15, 2026 | Form 4868 | October 15, 2026 |
Important note: March 15 falls on a Sunday in 2026, so the deadline shifts to Monday, March 16. Mark that date on your calendar now.
What a Business Tax Extension Actually Does (And Doesn’t Do)
Extension = More Time to File, Not More Time to Pay
This is the most common misconception I encounter. Form 7004 extends your filing deadline by six months. That’s it. It doesn’t extend your payment deadline by a single day.
If your S-Corp or partnership owes any tax (which is rare for pass-through entities, but possible), that payment was due by the original deadline. If you owe estimated taxes on your personal return because of K-1 income, those payments follow federal income tax deadlines too.
Interest starts accruing on any unpaid balance from the original due date. So filing an extension without paying what you owe just makes the problem bigger.
Why Extensions Are a Strategic Tool, Not a Failure
The extension paperwork takes 5 minutes. The planning to use those extra six months wisely? That’s where value gets created.
Here’s when a business tax extension makes strategic sense:
- Waiting for K-1s from other partnerships or S-Corps you invested in
- Complex transactions that need more analysis (business sale, merger, large asset purchase)
- Year-end planning opportunities still being finalized
- Catch-up bookkeeping in progress
- Major life event (divorce, death of partner, business transition)
Extensions aren’t failure. Extension without a plan is. The best extensions I file save clients money because we use that time to find deductions the March deadline would have missed.
S-Corporation Extension Deadline 2026
S-Corps file Form 1120-S and follow the earliest deadline of any business entity. Here’s what you need to know.
Original Deadline: March 16, 2026
Your S-Corp return is due the 15th day of the third month after your tax year ends. For calendar-year S-Corps (most of them), that’s March 15. But since March 15, 2026 falls on Sunday, you get until Monday, March 16, 2026.
By this date, you must either file your complete Form 1120-S or submit Form 7004 for an extension. If you do neither, penalties start immediately.
For more details on S-Corp filing requirements, see our S-Corp tax deadlines and filing requirements guide.
Extended Deadline: September 15, 2026
File Form 7004 by March 16, and your new deadline becomes September 15, 2026. That’s an automatic six-month extension. No approval needed. No explanation required. Just file the form on time.
Between March and September, you should be:
- Making quarterly estimated payments on K-1 income flowing to your personal return
- Working with your CPA on tax planning moves
- Gathering any missing documentation
- Reviewing reasonable compensation strategy for the following year
How to File Form 7004 for S-Corps
Filing a business tax extension isn’t complicated. Here’s the process:
Step 1: Gather your S-Corp’s EIN and basic information
You’ll need your Employer Identification Number, business name, address, and the tax year you’re extending.
Step 2: Complete Form 7004, checking box for Form 1120-S
Form 7004 asks which return you’re extending. For S-Corps, you’ll select Form 1120-S. You’ll also need to estimate any tax due (usually zero for S-Corps since they’re pass-through entities).
Step 3: Calculate and pay any estimated tax due
If your S-Corp has built-in gains tax, excess net passive income tax, or LIFO recapture tax, estimate and pay those amounts with your extension. Most S-Corps won’t owe anything at the entity level.
Step 4: File electronically or mail to the appropriate IRS address
E-filing is strongly recommended. You get instant confirmation that the IRS received your extension. Paper filing? You won’t know if it arrived until it’s too late to fix problems.
Step 5: Keep confirmation for your records
Save your e-file confirmation or certified mail receipt. If the IRS later claims you didn’t file an extension, this proof is your protection.
For comprehensive S-Corp tax help, explore our S-Corp tax services.
Partnership Extension Deadline 2026 (Including Multi-Member LLCs)
Partnerships and multi-member LLCs taxed as partnerships follow the same deadline as S-Corps. Here’s what partnership owners need to know.
Original Deadline: March 16, 2026
Form 1065 (partnership return) is due March 15 for calendar-year partnerships. In 2026, that shifts to March 16 because March 15 lands on Sunday.
Why do partnerships file so early in tax season? Because partners need their K-1s to file personal returns. The IRS wants partnership returns done first so K-1s can flow through to individual filers.
For a deep dive on partnership filing, see our complete guide to partnership taxation.
Extended Deadline: September 15, 2026
Just like S-Corps, partnerships get an automatic six-month extension by filing Form 7004 on time. Your new deadline: September 15, 2026.
One ripple effect to consider: if your partnership extends to September, your partners won’t get their K-1s until fall. That means partners probably need to file personal extensions too. Make sure everyone in the partnership knows the timeline.
K-1 Distribution Requirements
Schedule K-1 must be provided to partners by the filing deadline. If you file on March 16, K-1s go out by March 16. If you extend to September 15, K-1s are due September 15.
Here’s where it gets expensive: late K-1 penalties are separate from late filing penalties. Miss both, and you’re stacking penalties on top of each other.
The 2026 penalty for late K-1 distribution is $330 per form. A 4-partner partnership that files late AND distributes K-1s late could face:
- Late filing penalty
- Plus late K-1 penalty times four partners
We’ll cover the math in detail below.
For K-1 specifics, check our Schedule K-1 Form 1065 guide and Form 1065 instructions.
C-Corporation Extension Deadline 2026
C-Corps follow a different timeline than pass-through entities because they’re taxed at the entity level.
Original Deadline: April 15, 2026
For calendar-year C-Corps, Form 1120 is due April 15, 2026. That’s one month later than S-Corps and partnerships.
C-Corps are more likely to owe taxes at the entity level since they don’t pass income through to shareholders. Make sure any estimated tax payments are made by April 15, even if you’re filing an extension.
Extended Deadline: October 15, 2026
C-Corps also get a six-month automatic extension via Form 7004, pushing the deadline to October 15, 2026.
The same rules apply: extension is for filing only, not payment. Any tax owed should be paid by April 15 to avoid interest and potential penalties.
For more on C-Corp requirements, read our guide on C-Corp tax filing deadlines.
Single-Member LLC & Sole Proprietor Deadlines
If you’re a single-member LLC or sole proprietor, your business taxes are reported on your personal return. That means different deadlines and a different extension form.
Original deadline: April 15, 2026 Extended deadline: October 15, 2026 Extension form: Form 4868 (NOT Form 7004)
Single-member LLCs report business income on Schedule C of Form 1040. Since it’s part of your personal return, you use the personal extension form.
Form 4868 vs. Form 7004:
- Form 4868 = Personal returns and single-member LLCs
- Form 7004 = Business returns (S-Corps, partnerships, C-Corps, multi-member LLCs)
Don’t file the wrong form. If you’re a single-member LLC and file Form 7004, the IRS won’t process it as a valid extension for your Schedule C.
For personal extension tips, see our personal tax extension guide.
What Happens If You Miss the Extension Deadline
This is where things get expensive fast. Pass-through entity penalties are per-shareholder or per-partner, which means they multiply quickly.
S-Corp & Partnership Late Filing Penalties
The 2026 penalty for filing Form 1120-S or Form 1065 late is $245 per shareholder or partner per month. Maximum duration: 12 months.
That penalty applies even if your S-Corp or partnership owes zero tax. The IRS doesn’t care that pass-through entities don’t pay tax at the entity level. Miss the deadline, pay the penalty.
Example: A 3-shareholder S-Corp that files 5 months late faces:
$245 × 3 shareholders × 5 months = $3,675 in penalties
And that’s before any K-1 penalties.
The K-1 Penalty Stack: It Adds Up Fast
On top of late filing penalties, you face separate penalties for late K-1 distribution. The 2026 rate is $330 per late K-1.
So that same 3-shareholder S-Corp would also owe:
$330 × 3 shareholders = $990 in K-1 penalties
Combined total: $4,665 in penalties for a company that owed zero tax.
Real Example: How Penalties Compound
Let’s walk through a realistic scenario:
- 4-partner real estate partnership
- Files Form 1065 three months late
- K-1s distributed late to all partners
Late filing penalty: $245 × 4 partners × 3 months = $2,940
Late K-1 penalty: $330 × 4 partners = $1,320
Total exposure: $4,260
I’ve seen partnerships pay more in penalties than they would have paid a CPA to file on time. Don’t be that partnership.
How to Get Penalty Relief
If you’ve already missed a deadline, all isn’t lost. The IRS offers several penalty relief options.
First Time Penalty Abatement (FTA)
First Time Penalty Abatement is your best option if you qualify. Requirements:
- Clean 3-year compliance history: No penalties assessed for the prior three tax years
- All required returns filed: You can’t request FTA if you have unfiled returns
- Current on payments: Any taxes owed must be paid or on an approved payment plan
You can request FTA by calling the IRS or submitting a written request. Many taxpayers don’t know this option exists, so they pay penalties they could have avoided.
Pro tip: First Time Abatement is your get-out-of-jail-free card. But you only get one. Use it wisely.
Reasonable Cause Relief
If you don’t qualify for FTA, you can request penalty abatement based on reasonable cause. The IRS accepts penalty relief for circumstances beyond your control:
- Natural disaster affecting your area
- Serious illness or hospitalization
- Death of immediate family member
- Fire, casualty, or other disaster that destroyed records
- IRS error or incorrect advice from an IRS employee
What doesn’t qualify: “I forgot,” “I was too busy,” or “My CPA didn’t remind me.” Those aren’t reasonable cause.
You’ll need documentation: medical records, insurance claims, FEMA declarations, or other proof of the circumstances that prevented timely filing.
Filing Form 843
Form 843 is the formal request for penalty abatement. Complete the form, attach your supporting documentation, and submit to the IRS service center that issued the penalty notice.
Include a clear written explanation of why you missed the deadline and why the IRS should abate the penalty. Specific details matter more than lengthy explanations.
For complex penalty situations, our tax resolution services can help you navigate the process.
Texas-Specific Considerations
Texas doesn’t have a state income tax, but it does have a franchise tax. Here’s what Texas business owners need to know.
The Texas franchise tax extension generally aligns with your federal extension. If you extend your federal return, your Texas franchise tax return extends automatically.
However, if you need a separate Texas extension, file Form 05-164 with the Texas Comptroller. Electronic filing is available through the Comptroller’s website.
The franchise tax isn’t based on income the same way federal taxes are. It’s based on margin (revenue minus certain deductions). Even if your business shows a loss federally, you might owe Texas franchise tax.
For Texas-specific guidance, work with a Texas CPA firm that understands both federal and state requirements.
When Extension Is the Right Strategy
Extension isn’t failure. Extension without a plan is.
Here’s my perspective on when filing a business tax extension makes sense:
Good reasons to file an extension:
- Waiting for K-1s from other investments. If you’re a partner in multiple entities, you can’t file until you receive all your K-1s. Some partnerships extend to September, which means your K-1 won’t arrive until fall.
- Complex transaction that needs analysis. Major asset sales, mergers, business restructuring, or real estate exchanges require careful planning. Rushing the return to meet a March deadline can cost you deductions.
- Year-end planning still being optimized. Maybe you’re finalizing retirement contributions, vehicle purchases, or equipment decisions that affect your 2025 return.
- Catch-up bookkeeping. If your books aren’t closed, you can’t file an accurate return. Better to extend and get the numbers right than rush and amend later.
- Major life changes. Divorce, death of a business partner, or selling the business all create complex tax situations that benefit from extra time.
Not good reasons:
- Procrastination. Extension without a plan just delays the inevitable.
- Avoiding paying taxes you owe. Extension doesn’t delay payment. You’ll just add interest to your bill.
- Your CPA is too busy. If your CPA can’t fit you in, that’s a process problem. Find a better CPA.
The best extensions I file save clients money because we use that time to find deductions, optimize tax planning, and structure transactions properly. The March deadline would have forced us to leave money on the table.
Frequently Asked Questions
When are S corp taxes due with extension in 2026?
S-Corp taxes (Form 1120-S) are originally due March 16, 2026. With a valid Form 7004 extension filed by that date, the extended deadline is September 15, 2026.
Do I still have to pay taxes if I file an extension?
Yes. An extension gives you more time to file your return, not more time to pay taxes owed. Any estimated tax due must be paid by the original deadline (March 16 for S-Corps and partnerships, April 15 for C-Corps) to avoid interest and potential penalties.
What form do I file for a business tax extension?
Use Form 7004 for S-Corps (Form 1120-S), partnerships (Form 1065), multi-member LLCs, and C-Corps (Form 1120). Single-member LLCs and sole proprietors use Form 4868 since they file on personal returns.
Can I get another extension after September 15?
Generally, no. The IRS does not grant additional extensions beyond the automatic 6-month extension. If you miss the extended deadline, file as soon as possible to minimize penalties, which accrue monthly.
What are the penalties for late S corp filing?
The 2026 penalty is $245 per shareholder per month, up to 12 months. A 3-shareholder S-Corp filing 6 months late would face $4,410 in penalties ($245 × 3 × 6). Additional K-1 late penalties of $330 per form may also apply.
How do I file Form 7004?
You can e-file Form 7004 through IRS-approved software or a tax professional, or mail a paper form to the appropriate IRS service center. E-filing is recommended because you receive immediate confirmation. The form requires your business name, EIN, tax year, and the specific return you’re extending.
What’s the difference between Form 4868 and Form 7004?
Form 4868 extends personal tax returns (Form 1040), including single-member LLCs and sole proprietors who report on Schedule C. Form 7004 extends business returns including S-Corps (1120-S), partnerships (1065), C-Corps (1120), and multi-member LLCs.
Does Texas have a separate business tax extension?
Texas doesn’t have a state income tax, but it does have a franchise tax. The franchise tax extension generally follows federal extension deadlines. File Form 05-164 with the Texas Comptroller if you need additional time.
Next Steps
If you need help filing your business tax extension:
We handle Form 7004 extensions as part of our tax preparation services. The extension itself takes minutes to file. The planning to use those six months wisely takes expertise.
If you’ve already missed a deadline:
Penalties add up fast, but relief options exist. We can help you file late returns and request penalty abatement through First Time Abatement or reasonable cause relief.
If you want proactive tax planning:
The best way to avoid extension stress? Work with a CPA who calls you in October, not March. That’s when the real planning happens.
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Ready to get started? Schedule a consultation and let’s make sure your 2026 tax deadlines go smoothly.