When Are Small Business Taxes Due? Your 2026 Tax Calendar

A Houston restaurant owner walked into our office last March holding a notice from the IRS. She’d missed the deadline for her S-Corp return by eleven days. The penalty: $220 per shareholder, per month. With three shareholders, that was $660 for a filing she thought wasn’t due until April.

She didn’t owe additional taxes. Her bookkeeping was clean. She simply had the wrong date on her calendar.

Tax deadlines vary by business structure, and the penalties for missing them accumulate fast. This calendar covers every date a small business owner needs to know for the 2026 tax year.

January 2026: The Year Starts with Deadlines

January 15: Q4 2025 Estimated Tax Payment

The fourth quarter estimated tax payment for the 2025 tax year is due January 15, 2026 (a Thursday). This covers income earned from September 1 through December 31, 2025.

There is an exception: if a taxpayer files their 2025 return and pays the full balance by January 31, the Q4 estimated payment can be skipped.

January 31: W-2 and 1099-NEC Distribution

Employers must furnish W-2 forms to employees by January 31. Because January 31, 2026 falls on a Saturday, the deadline shifts to Monday, February 2, 2026.

The same adjusted deadline applies to 1099-NEC forms for independent contractors paid $600 or more during 2025.

These forms must also be filed with the IRS/SSA by that date.

March 2026: Partnership and S-Corp Returns

March 16: Form 1065 and Form 1120-S

Partnerships file Form 1065 and S-corporations file Form 1120-S by the 15th day of the third month after their tax year ends. For calendar-year entities, that’s March 15, but March 15, 2026 falls on a Sunday, so the deadline moves to Monday, March 16, 2026.

Schedule K-1 forms must also be distributed to partners and shareholders by this date. These forms report each owner’s share of income, deductions, and credits, and are essential for filing personal returns.

Extension option: Filing Form 7004 by March 16 grants an automatic six-month extension, pushing the deadline to September 15, 2026. However, any estimated tax owed is still due by the original date.

April 2026: The Big One

April 15: Individual Returns (Form 1040)

Sole proprietors, single-member LLCs, and freelancers report business income on Schedule C as part of their individual Form 1040. That return is due April 15, 2026 (a Wednesday).

This deadline also applies to:

C-corporation returns (Form 1120) for calendar-year corporations
First quarter 2026 estimated tax payment (Form 1040-ES)
Trust and estate returns (Form 1041)

For self-employed individuals, April 15 carries a triple obligation: file last year’s return, pay any remaining balance, and make the first quarterly payment for the current year.

Extension option: Filing Form 4868 extends the filing deadline to October 15, 2026. Filing Form 7004 extends corporate returns by six months. Again, extensions only apply to filing, not to payment. Any tax owed must still be paid by April 15 to avoid interest and penalties.

The 2026 Estimated Tax Calendar

Self-employed individuals and business owners who expect to owe $1,000 or more in federal taxes typically need to make quarterly estimated tax payments. Here are the 2026 dates:

Quarter	Income Period	Due Date
Q1	January 1 – March 31	April 15, 2026
Q2	April 1 – May 31	June 15, 2026
Q3	June 1 – August 31	September 15, 2026
Q4	September 1 – December 31	January 15, 2027

The quarters are not evenly split. Q2 covers only two months while Q3 covers three. This catches many first-time filers off guard. The June payment arrives quickly after April’s.

Estimated payments are made using Form 1040-ES and can be submitted through IRS Direct Pay at irs.gov/payments, the EFTPS system, or the IRS2Go mobile app.

May 2026: Texas Franchise Tax

May 15: Texas Franchise Tax Report

Texas may not have a state income tax, but it does have a franchise tax (often called the “margin tax”). The annual franchise tax report is due May 15, 2026 (a Friday).

For the 2026 report year, businesses with annualized total revenue at or below $2.65 million owe no franchise tax. However, even businesses below this threshold must file a Public Information Report or Ownership Information Report with the Texas Comptroller.

A $50 penalty applies to each report filed after the due date. If tax is owed and paid 1–30 days late, a 5% penalty is assessed. After 30 days, the penalty increases to 10%.

September and October 2026: Extended Returns

September 15: Extended Partnership and S-Corp Returns

Partnerships and S-corporations that filed extensions in March must submit their returns by September 15, 2026.

This date also coincides with the Q3 estimated tax payment.

October 15: Extended Individual and C-Corp Returns

Individual returns and C-corporation returns on extension are due October 15, 2026 (a Thursday).

What Happens When You Miss a Deadline

The IRS assesses different penalties depending on what was missed.

Failure-to-File Penalty

The penalty for filing late is 5% of the unpaid tax for each month (or partial month) the return is late, up to a maximum of 25%. If a return is more than 60 days late, the minimum penalty is the lesser of $525 or 100% of the tax owed.

This is the most expensive common penalty, and it’s why filing on time, even without full payment, is critical.

Failure-to-Pay Penalty

The penalty for paying late is 0.5% of the unpaid tax per month, up to 25%. This is significantly lower than the failure-to-file penalty, which is why tax professionals consistently advise: file on time, even if the money isn’t there yet.

When both penalties apply in the same month, the combined rate is 5% (4.5% for late filing plus 0.5% for late payment).

Estimated Tax Underpayment Penalty

For Q1 2026, the IRS underpayment interest rate is 7% per year, compounded daily. This rate is based on the federal short-term rate plus 3 percentage points. The IRS adjusts this rate quarterly, so it may change throughout 2026.

The underpayment penalty can be avoided by meeting any of these conditions:

Owing less than $1,000 after withholding and credits
Paying at least 90% of the current year’s tax liability
Paying at least 100% of the prior year’s tax liability (110% if prior year AGI exceeded $150,000)

The third option, often called “safe harbor,” is the simplest protection for business owners with variable income.

Partnership and S-Corp Late Filing Penalty

Partnerships and S-corporations face a penalty of $220 per partner/shareholder per month (or partial month) the return is late, up to 12 months. A four-partner LLC that files three months late would owe $2,640, even if no tax is due.

Texas-Specific Considerations

Houston business owners benefit from having no state income tax, which means no quarterly estimated payments to the state. However, there are a few Texas-specific items to track:

Texas franchise tax is due May 15, regardless of federal filing deadlines
Sales tax filings follow their own schedule (monthly, quarterly, or annually depending on volume)
Businesses with nexus in other states may owe income tax and estimated payments to those states, each with its own deadlines

A Houston contractor who takes jobs in Louisiana, for example, may owe Louisiana state income tax on that work. Multi-state tax obligations add complexity that is easy to overlook.

The Complete 2026 Deadline Summary

Date	What’s Due
Jan 15, 2026	Q4 2025 estimated tax payment
Feb 2, 2026	W-2 and 1099-NEC forms (adjusted from Jan 31)
Mar 16, 2026	Partnership (1065) and S-Corp (1120-S) returns
Apr 15, 2026	Individual (1040), C-Corp (1120) returns; Q1 2026 estimated payment
May 15, 2026	Texas franchise tax report
Jun 15, 2026	Q2 2026 estimated tax payment
Sep 15, 2026	Extended 1065/1120-S returns; Q3 2026 estimated payment
Oct 15, 2026	Extended 1040/1120 returns
Jan 15, 2027	Q4 2026 estimated tax payment

How to Stay Ahead of Deadlines

Most penalty situations stem from the same root cause: a business owner who thought they had more time. The restaurant owner who missed her S-Corp deadline assumed March 15 and April 15 were the same. A sole proprietor who forgot the June estimated payment didn’t realize Q2 was only two months.

Clean, current bookkeeping is the foundation. When financial records are up to date, calculating estimated payments takes minutes instead of a scramble. When tax documents are organized throughout the year, filing by the deadline becomes straightforward rather than stressful.

At EZQ Group, we help Houston business owners stay ahead of every deadline on this calendar. From quarterly estimated tax calculations to annual return preparation, our team handles the timeline so business owners can focus on running their businesses.

Concerned about upcoming deadlines? Learn about our tax preparation services or contact us to get started.

This article provides general tax information current as of February 2026. Tax deadlines can shift when they fall on weekends or federal holidays, and the IRS occasionally grants extensions for disaster areas. Consult a qualified tax professional for advice specific to your situation. Sources: IRS Publication 509 (2026), IRS Quarterly Interest Rates, Texas Comptroller: Franchise Tax.