When Are Corporate Taxes Due in 2026: All Key Deadlines by Entity Type
Key Takeaways
- S corp (Form 1120-S) and partnership (Form 1065) returns for tax year 2025 are due March 16, 2026. March 15 falls on a Sunday in 2026.
- C corp (Form 1120) returns for tax year 2025 are due April 15, 2026.
- A tax extension gives more time to FILE, not more time to PAY. Estimated taxes are still due on the original deadline. Underpayment triggers penalties and interest from the original due date.
- Corporate estimated quarterly tax payments for tax year 2026 are due April 15, June 15, September 15, and December 15.
- W-2 and 1099-NEC forms must be issued to recipients and filed with the IRS by January 31. In 2026, January 31 falls on a Saturday, shifting the deadline to Monday February 2, 2026.
2026 Corporate Tax Deadlines: Full Calendar
S Corp vs C Corp: The Deadline Difference That Catches Founders
This is the most common 2026 tax deadline mistake: assuming corporate taxes follow the April 15 individual return schedule.
S corp and partnership returns are due March 15 each year, not April 15. The reason is structural: S corp and partnership returns flow through to individual shareholders and partners who need the K-1 forms from their business before they can file their personal returns. If S corp returns were due April 15 like individual returns, partners and shareholders could not complete their personal filings on time.
In 2026, March 15 falls on a Sunday. The S corp filing deadline shifts to Monday March 16, 2026.
A founder running an S corp who prepares for an April 15 deadline is one month late. Penalties for late filing start at 5% of unpaid tax per month, up to 25% maximum. For a first-year S corp founder who misses this date because they confused it with the individual deadline, it is an entirely avoidable cost.
The Extension Trap: More Time to File, Not to Pay
An extension is not more time to pay. This is the single most important thing to understand about tax extensions.
Filing Form 7004 by the original deadline gives S corps an additional six months to file the return, moving the deadline from March 16 to September 15, 2026. C corps get an additional six months, moving from April 15 to October 15, 2026.
What the extension does not do: give more time to pay taxes owed.
If a company owes $50,000 in taxes for the 2025 tax year and files an extension on March 16 without paying that $50,000, the IRS charges underpayment penalties and interest from March 16 onward. By October 15 when the extended return is filed, the penalty and interest balance has been accumulating for six months.
The rule: estimate taxes owed, pay that estimate by the original deadline, then file the complete return during the extension period when all the numbers are final. Never treat an extension as a payment deferral. It is not one.
Estimated Quarterly Tax Payments in 2026
Corporations are generally required to pay estimated taxes quarterly throughout the year rather than in one lump sum at filing time. For calendar year corporations paying taxes on 2026 income, the four estimated payment dates are:
- Q1: April 15, 2026
- Q2: June 15, 2026
- Q3: September 15, 2026
- Q4: December 15, 2026
The IRS safe harbor rule for corporations: pay either 100% of the prior year's tax liability or 100% of the current year's estimated liability across four equal installments. Meeting safe harbor protects against underpayment penalties even if the final return shows more tax is owed.
Missing a quarterly payment does not result in a separate penalty but contributes to an underpayment penalty calculated on the unpaid balance from the missed due date through the actual payment date.
State Tax Deadlines
Most states conform to federal corporate tax deadlines but not all. Common variations:
- California has its own tax calendar that generally aligns with federal dates but applies California's corporate minimum tax ($800 annually for LLCs and corporations) separately.
- New York follows federal deadlines for most entity types but has its own franchise tax structure.
- Texas, Nevada, and Wyoming have no state corporate income tax but may have gross receipts or franchise tax obligations with separate filing schedules.
Confirm your state's specific deadlines with your CPA or your state's department of revenue, as state rules vary significantly and change more frequently than federal deadlines.
How to Be Tax-Ready Before Every Deadline
The fastest way to miss a tax deadline is to arrive at February with twelve months of uncategorized transactions and a year-end close that has not happened yet.
For founders on QuickBooks Online, tax readiness depends on the books being clean and closed before the filing deadline, not on the same weekend as it. Founders who have structured bookkeeping automation in QuickBooks Online throughout the year arrive at each deadline with categorized, reconciled data rather than a reconstruction project. And since the year-end close is what produces the financial statements the CPA needs to prepare the return, having month-end close automation in place means December close happens in early January rather than late February.
Finlens runs on top of QuickBooks Online with no migration and automates the categorization and reconciliation that makes tax preparation fast rather than a scramble.
Before Finlens: Tax season arrives. Books are three months behind. The CPA requests clean financial statements. Alot of time is spent on cleanup before the actual return can be prepared.
After Finlens: Books close cleanly every month. Year-end statements are ready within days of December 31. The March 16 S corp deadline becomes a calendar event, not a deadline crisis.
When are corporate taxes due in 2026 is a question with specific answers. Being ready for those answers before the deadline is what the rest of the year is for.
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FAQ
When are S corp taxes due in 2026?
S corp returns (Form 1120-S) for tax year 2025 are due March 16, 2026. The standard March 15 deadline shifts to March 16 because March 15, 2026 falls on a Sunday.
When are C corp taxes due in 2026?
C corp returns (Form 1120) for tax year 2025 are due April 15, 2026.
When is the S corp extension deadline in 2026?
S corps that file for an extension on March 16, 2026 have until September 15, 2026 to file the complete return.
When is the C corp extension deadline in 2026?
C corps that file for an extension on April 15, 2026 have until October 15, 2026 to file the complete return.
Does filing a tax extension give more time to pay?
No. A tax extension gives more time to file the return, not more time to pay taxes owed. Estimated taxes are still due on the original filing deadline. Underpayment after the original deadline triggers penalties and interest regardless of whether an extension was filed.
When are 2026 corporate estimated quarterly tax payments due?
Q1: April 15, 2026. Q2: June 15, 2026. Q3: September 15, 2026. Q4: December 15, 2026.
When are W-2 and 1099-NEC forms due in 2026?
January 31, 2026 is the standard deadline to issue W-2s to employees and 1099-NECs to contractors. Because January 31, 2026 falls on a Saturday, the deadline shifts to Monday February 2, 2026.
