Navigating tax deadlines is one of the hardest parts of running a business, especially for founders juggling multiple entities or filing in the U.S. for the first time. The forms you file and the dates you owe them depend entirely on how your business is structured.
Whether you operate as a sole proprietorship, partnership, limited liability company (LLC), S Corporation (S corp), or C Corporation (C corp), this guide breaks down every federal, state, and franchise tax deadline you need to know for 2026, along with the penalties for missing them and how to buy more time with an extension.
Key Takeaways
- Your filing deadline depends on your entity type: S corps and partnerships file by March 16, 2026, while C corps, sole proprietors, and single-member LLCs file by April 15, 2026.
- An extension (Form 7004 for businesses, Form 4868 for individuals) gives you more time to file, not more time to pay. Any tax you owe is still due on the original deadline.
- Missing a deadline is expensive: a late Form 5472 carries a $25,000 penalty, and Delaware adds a $200 penalty plus 1.5% monthly interest on unpaid franchise tax.
Which Tax Forms You Need Based on Your Business Structure
Your business structure determines which return you file and when it is due. Here is how the four main groups break down.
Sole Proprietors and Single-Member LLCs
Report business income and expenses on Schedule C, filed with your personal return (Form 1040). The IRS treats a single-member LLC as a disregarded entity by default, so its income flows onto your 1040.
Partnerships and Multi-Member LLCs
File an informational return (Form 1065) and issue a Schedule K-1 to each partner or member showing their share of profit or loss. Most multi-member LLCs are taxed as partnerships by default. Learn more in our guide to LLC taxes.
S Corporations
S corps file Form 1120-S and provide shareholders with a Schedule K-1 for their personal returns. As a pass-through entity, the S corp itself generally pays no federal income tax.
C Corporations
C corps file Form 1120 and are taxed as separate entities, which can lead to double taxation on profits and dividends. If you need a hand, Cleer offers C corporation tax preparation.
Key Business Tax Deadlines for 2026
Several 2026 dates shift because the usual deadline lands on a weekend. The dates below already reflect those adjustments.
- February 2: Deadline to provide W-2s to employees, 1099-NEC forms to contractors, and file Form 940 (Federal Unemployment Tax Return). The usual January 31 date falls on a Saturday in 2026.
- March 1: C Corporation Delaware Franchise Tax and Annual Report filing and payment due.
- March 16: S Corporation (Form 1120-S) and Partnership (Form 1065) returns and extensions due. The usual March 15 date falls on a Sunday in 2026.
- April 15: Individual (Form 1040) and C Corporation (Form 1120) returns and extensions due, plus first-quarter 2026 estimated tax payments.
- June 1: LLC Delaware Franchise Tax payment due.
- June 15: Second-quarter 2026 estimated tax payments due.
- September 15: Third-quarter 2026 estimated tax payments due, and the extended deadline for S Corporation and Partnership returns.
- October 15: Extended deadline for Individual and C Corporation returns.
- December 15: Fourth-quarter 2026 estimated tax payments due for C corporations.
Fiscal Year Deadlines
If your business does not use a December 31 year-end, your deadlines shift accordingly, so it’s best to check the IRS website for the correct dates. Keep these fiscal-year rules in mind as you plan for 2026.
Standard Fiscal Year Rule (3.5 Months After Year-End)
A C corporation’s return is generally due the 15th day of the 4th month after its tax year ends, which works out to roughly 3.5 months. A September 30 year-end, for example, produces a January 15 deadline.
Pass-through entities file earlier: S corporations and partnerships are due the 15th day of the 3rd month after year-end, closer to 2.5 months out.
June Fiscal Year-End Exception
A special rule gives C corporations with a June 30 year-end a September 15 due date, the 15th day of the 3rd month, for tax years beginning before January 1, 2026. For tax years beginning on or after January 1, 2026, the standard rule applies, and the return is generally due on the 15th day of the 4th month after the end of the tax year.
Common Non-Calendar Fiscal Years
Beyond June 30, we regularly see a March 31 year-end for UK-related companies and a January 31 year-end for tech companies that model themselves on Salesforce. Each one shifts your federal and state deadlines to match the 15th-day rule for your entity type.
Dissolution Deadlines
When a company closes, its final return is due based on a short tax year ending in the month it formally dissolves with the state. For a full walkthrough, see our guide on how to dissolve your corporation.
Quarterly Estimated Tax Payments
Self-employed individuals and pass-through owners generally must make quarterly estimated tax payments if they expect to owe $1,000 or more in tax for the year. Corporations use a lower threshold and must generally pay estimated tax if they expect to owe $500 or more. The 2026 deadlines are:
- April 15, 2026
- June 15, 2026
- September 15, 2026
- December 15, 2026 for C corporations
- January 15, 2027 for individuals, partnerships, and S corporation owners
Extension Requests
Need more time? Both businesses and individuals can get an automatic extension, but remember that an extension gives you more time to file, not more time to pay. Any tax owed is still due on the original deadline, and interest and penalties accrue from that date.
Form 7004 for Businesses
Businesses request an automatic 6-month extension with Form 7004, filed by the original return due date: March 16, 2026 for partnerships, multi-member LLCs, and S corps; April 15, 2026 for C corps. This is a service we provide free to our clients.
Pro tip💡: Missing a filing date can result in complications with the IRS. If you need help filing for an extension and would like to speak with an expert, contact us today.
Form 4868 for Individuals
Sole proprietors and single-member LLC owners request an automatic 6-month extension with Form 4868, filed by April 15, 2026. This moves the filing deadline to October 15, 2026.
Extension Deadlines by Entity Type
- S corporations and partnerships: file Form 7004 by March 16, 2026, extended deadline September 15, 2026.
- C corporations: file Form 7004 by April 15, 2026, extended deadline October 15, 2026.
- Individuals, sole proprietors, and single-member LLCs: file Form 4868 by April 15, 2026, extended deadline October 15, 2026.
Penalties for Missing a Deadline
Missing a deadline can be costly, and for foreign-owned businesses the information-return penalties are among the steepest in the U.S. tax code.
Here is what is at stake.
Late-Filing Penalties (Form 5472, Form 5471, FBAR, Form 8938)
- Form 5472: $25,000 per form for failing to file, filing late, or filing a substantially incomplete return, with an additional $25,000 for each 30-day period the failure continues after IRS notice, and no maximum. This filing is most relevant to foreign-owned single-member LLCs and 25% foreign-owned U.S. corporations.
- Form 5471: $10,000 per form, per year for U.S. persons who fail to report ownership in a foreign corporation, with additional penalties if the failure continues after IRS notice.
- FBAR (FinCEN Form 114): the non-willful penalty starts at a $10,000 statutory base, adjusted for inflation to up to $16,536 per report for 2026. Willful violations carry far higher penalties.
- Form 8938: $10,000 for failing to report specified foreign financial assets, with additional penalties of up to $50,000 if the failure continues after IRS notice.
Delaware Late Filing Fees and Penalties
A Delaware corporation that misses the March 1 franchise tax and annual report deadline owes a $200 late penalty plus 1.5% monthly interest on the unpaid balance. A Delaware LLC that misses the June 1 deadline owes the same $200 penalty.
Beyond the fees, a late filing puts your entity out of good standing, which can block financing, contracts, and M&A activity until you cure it.
State and Franchise Tax Deadlines
Federal deadlines are only half the picture. Your state of incorporation, and any state where you do business, sets its own filing and franchise tax dates.
State Filing Deadline Variations
State income tax filing deadlines often mirror the federal dates, but not always. Check with your state of incorporation and any states where you have a tax presence, since due dates, extension rules, and minimum taxes vary widely.
Franchise Tax Deadlines by State (e.g., Delaware vs. California)
Franchise tax deadlines depend on where you incorporated the business. In Delaware, C corporations must file the annual report and pay franchise tax by March 1, 2026, while LLCs pay by June 1, 2026. Watch out: March 1, 2026 falls on a Sunday, and Delaware does not move the corporate deadline, so plan to file in the last week of February.
In California, C corporations generally file Form 100 by April 15, 2026 for calendar-year filers and are generally subject to an $800 minimum franchise tax.
How Cleer Tax Can Help You Meet Every Deadline
At Cleer Tax, our team is built around the needs of U.S. startups and foreign-owned businesses. We provide comprehensive tax preparation and advisory services covering federal, state, and franchise filings, so you never have to track these dates alone.
Our Corporate Income Tax Packages bundle federal and state income tax filings into one flat-rate, hassle-free service tailored to U.S. businesses and subsidiaries.
If you need help reducing your tax liability or managing your books, contact us or visit our pricing page.
Frequently Asked Questions (FAQ)
When are C corp taxes due?
Calendar-year C corporations file Form 1120 by April 15, 2026. With a Form 7004 extension, the deadline moves to October 15, 2026, but any tax owed is still due April 15.
When are business taxes due?
It depends on your structure. S corporations and partnerships file by March 16, 2026. C corporations, sole proprietors, and single-member LLCs file by April 15, 2026.
When are LLC taxes due?
A single-member LLC reports on Schedule C with Form 1040 by April 15, 2026. A multi-member LLC files Form 1065 by March 16, 2026. An LLC taxed as an S corp files Form 1120-S by March 16, 2026.
When is Form 1120-S due?
Form 1120-S is due March 16, 2026, for calendar-year S corporations, since March 15 falls on a Sunday. A Form 7004 extension moves the deadline to September 15, 2026.
When are corporate tax returns due with an extension?
With Form 7004, C corporation returns are due October 15, 2026, and S corporation returns are due September 15, 2026. The extension covers filing only, not payment.
Note: This article is for general informational purposes and isn’t tax, legal, or accounting advice. Tax rules change often, and your situation may differ. Talk to a Cleer Tax advisor before making decisions based on this content.
