Deadlines
Business tax deadlines 2026: every federal due date by entity type
When business taxes are due in 2026: partnerships and S corps by March 16, sole proprietors and C corps by April 15, extensions to September 15 and October 15, plus estimated tax, payroll and 1099 dates, in one table from IRS Publication 509.
Prepared by Aldro Accounting · Updated · Sources checked
The quick answer
For calendar-year 2025 returns, the IRS deadline was March 16, 2026 for partnerships (Form 1065) and S corporations (Form 1120-S), and April 15, 2026 for sole proprietors (Form 1040 with Schedule C) and C corporations (Form 1120). A 6-month extension (Form 7004 for businesses, Form 4868 for individuals) moves filing to September 15 or October 15, 2026, but not the payment date. Form W-2 and Form 1099-NEC were due February 2, 2026.
Annual return deadlines by business type
Partnerships and S corporations file by the 15th day of the 3rd month after their tax year ends. Individuals, including sole proprietors, and C corporations file by the 15th day of the 4th month. A C corporation with a fiscal year ending June 30 is the exception: it files by the 15th day of the 3rd month.
Scroll sideways to see all columns.
| Business type | Return | Due date | Extension form | Extended due date |
|---|---|---|---|---|
| Partnership or multi-member LLC | Form 1065, with a Schedule K-1 for each partner | March 16, 2026 | Form 7004 | September 15, 2026 |
| S corporation | Form 1120-S, with a Schedule K-1 for each shareholder | March 16, 2026 | Form 7004 | September 15, 2026 |
| Sole proprietor or single-member LLC | Form 1040 or 1040-SR with Schedule C | April 15, 2026 | Form 4868 | October 15, 2026 |
| C corporation | Form 1120 | April 15, 2026 | Form 7004 | October 15, 2026 |
In 2026, March 15 fell on a Sunday, so calendar-year partnerships and S corporations had until March 16, 2026. Whenever a due date falls on a Saturday, Sunday or legal holiday, the next business day counts.
Extensions move filing, not payment
Form 7004 gives partnerships, S corporations and C corporations an automatic 6-month extension of time to file. Individuals use Form 4868. Publication 509 tells corporations and individuals to pay what they estimate they owe with the extension request to avoid penalties and interest.
An S corporation must pay any tax due in full by the original due date, not counting extensions.
The S corporation election date
A calendar-year corporation that wanted S corporation treatment starting in 2026 had to file Form 2553 by March 16, 2026. Publication 509 says that if Form 2553 is filed late, S corporation treatment begins with calendar year 2027.
2026 estimated tax deadlines
Owners of sole proprietorships, partnerships and S corporations generally pay estimated tax on Form 1040-ES. The 2026 installments are due April 15, June 15 and September 15, 2026 and January 15, 2027.
A C corporation makes estimated tax installments if it expects its total tax for the year to be $500 or more. They are due by the 15th day of the 4th, 6th, 9th and 12th months of the tax year: April 15, June 15, September 15 and December 15, 2026 for a calendar-year corporation. A corporation that owes $500 or more and didn't pay at least the smaller of its current-year or prior-year tax on time is generally subject to the underpayment penalty figured on Form 2220.
Payroll and information return deadlines in 2026
Because January 31, 2026 fell on a Saturday, several January deadlines moved to Monday, February 2, 2026.
Deposits and e-filing
Corporations must make all federal tax deposits by electronic funds transfer, through EFTPS or the IRS business tax account. EFTPS takes same-day payments of $1 million or less submitted before 3:00 p.m. Eastern time on a business day. Larger payments must be submitted by 8:00 p.m. Eastern time the day before the due date.
Corporations must e-file Form 1120 if they file 10 or more returns of any type during the calendar year. The 10-return threshold for information returns such as Forms 1099 counts all information returns together.
What a missed deadline costs
A C corporation that files late may be penalized 5% of the unpaid tax for each month or part of a month, up to 25%. For a return required to be filed in 2026 that is more than 60 days late, the minimum is the smaller of the tax due or $525. Late payment adds half of 1% of the unpaid tax a month, up to 25%. When both apply in the same month, the late filing penalty is reduced by the late payment penalty.
A late Form 1065 or Form 1120-S is penalized per owner instead: for returns due after December 31, 2025, the base rate is $255 for each partner or shareholder for each month or part of a month, up to 12 months.
Aldro's flat yearly price covers everything tax for the year, including extensions. Our team works out the quarterly estimated tax amounts and tells you what to pay and when.
Worked example
Say a calendar-year S corporation with 2 shareholders misses March 16, 2026 and files on May 1, 2026 without an extension. That is 1 full month and part of a 2nd, so the penalty is $255 x 2 shareholders x 2 months = $1,020. A Form 7004 filed by March 16 would have moved the filing deadline to September 15, 2026. A C corporation that owes $8,000 and files its 2025 Form 1120 two months late, paying with the return, owes half of 1% x $8,000 x 2 = $80 for late payment. When both penalties apply, the IRS reduces the late filing penalty by the late payment penalty, so late filing is 4.5% x $8,000 x 2 = $720. Together that is $800, before interest.
Common questions
When are business taxes due in 2026?
For calendar-year 2025 returns: March 16, 2026 for partnerships and S corporations, and April 15, 2026 for sole proprietors and C corporations.
When is the LLC tax deadline?
It depends on how the LLC is taxed. A multi-member LLC taxed as a partnership files Form 1065 by March 16, 2026. A single-member LLC reports on Schedule C, due with the owner's Form 1040 on April 15, 2026.
What is the extended business tax deadline for 2026?
September 15, 2026 for partnerships and S corporations that filed Form 7004, and October 15, 2026 for C corporations on Form 7004 and individuals on Form 4868.
When are C corporation estimated taxes due in 2026?
April 15, June 15, September 15 and December 15, 2026 for a calendar-year corporation that expects to owe $500 or more.
Why were W-2s and 1099-NECs due February 2, 2026?
The usual January 31 date fell on a Saturday in 2026, so it moved to the next business day, Monday, February 2.
The cheapest way to get your business taxes done: $399 flat.
Business tax filing is $399 USD a year, and it covers everything tax for that year.
How it works
- Tell us about your business. A two-minute form. No payment is collected through it.
- Get your next steps by email. We’ll email you the next steps within one business day. After you sign up we’ll send you a secure upload link for your documents.
- We file it. Our team prepares and files your return. Add bookkeeping for $20 a month if you want it.
What's included
$399 a year covers everything tax for that tax year.
- Every business return for the year. All the federal and state or provincial business returns you need for the tax year: Schedule C, 1065, 1120-S, 1120 and their state returns in the US; T2, or T1 with T2125, in Canada.
- More than one state. Multi-state returns are included at the same price.
- Your personal return. The owner’s personal return (1040 or T1) is included when it’s needed for the business income.
- Quebec. Quebec returns (CO-17, TP-1 and TP-80) are included. Our Quebec pages are in French, and our team works with you in English.
- Extensions and reminders. Extensions (Form 7004 or 4868) and quarterly estimate reminders are included.
- Information returns. 1099-NEC, T4/T4A and T5018 slips are included in the tax price.
- City and excise returns. City and local business tax returns, and state excise returns such as Washington B&O, are included in the yearly price.
- Franchise tax reports. State franchise tax reports, such as the Texas franchise tax report, are included.
- Estimated tax and instalment amounts. We work out your quarterly estimated tax payments in the US, or your CRA instalments in Canada, and tell you what to pay and when.
- Unfiled past years. Each unfiled prior-year return is $399 per tax year, the same flat price.
- Bookkeeping at $20 a month. Unlimited bank and card accounts, monthly reconciliation and monthly statements.
Basic inventory tracking for online stores, such as Shopify, is included. Full cost-of-goods reconciliation is quoted separately. Payroll processing and sales-tax filing aren’t included in bookkeeping. Prices are in USD. Our team prepares and files your return.
Sources
- IRS: Publication 509, Tax calendars (2026) · checked October 31, 2026
- IRS: Instructions for Form 1120 · checked October 31, 2026
- IRS: Instructions for Form 1120-S · checked October 31, 2026
- IRS: Instructions for Form 1065 · checked October 31, 2026
- IRS: Instructions for Schedule C · checked October 31, 2026
- IRS: Form 1040-ES (2026) · checked October 31, 2026
- IRS: Failure to file penalty · checked October 31, 2026
This guide explains general rules from the sources listed. It isn’t tax advice for your situation.