Failure to file
5% of unpaid tax per month, capped at 25%. For 1065 and 1120-S the penalty is per partner/shareholder, per month — a five-partner return filed three months late costs roughly $3,700.
Tax Center
US Tax Forms & 2026 Filing Deadlines
A single reference for the federal forms CPA firms file most — who files them, when they are due, what an extension buys you, and what it costs to miss.
Forms
Federal forms and 2026 due dates
Calendar-year filers. Fiscal-year entities follow the equivalent day of the corresponding month; state deadlines can differ.
Individual & fiduciary returns
| Form | Description | Who files | 2026 due date | Extended |
|---|---|---|---|---|
| 1040 | US Individual Income Tax Return | Individuals, sole proprietors (Schedule C) | April 15, 2026 | October 15, 2026 (Form 4868) |
| 1040-NR | Nonresident Alien Income Tax Return | Nonresident individuals with US-source income | April 15, 2026 | October 15, 2026 |
| 1040-ES | Estimated Tax for Individuals | Anyone owing $1,000+ not covered by withholding | Apr 15 · Jun 15 · Sep 15, 2026 · Jan 15, 2027 | No extension available |
| 709 | Gift (and GST) Tax Return | Donors above the annual exclusion | April 15, 2026 | October 15, 2026 |
Business & entity returns
| Form | Description | Who files | 2026 due date | Extended |
|---|---|---|---|---|
| 1065 | US Return of Partnership Income | Partnerships and multi-member LLCs | March 16, 2026 | September 15, 2026 (Form 7004) |
| 1120-S | Income Tax Return for an S Corporation | S corporations | March 16, 2026 | September 15, 2026 (Form 7004) |
| 1120 | US Corporation Income Tax Return | C corporations (calendar-year) | April 15, 2026 | October 15, 2026 (Form 7004) |
| 990 | Return of Organization Exempt From Income Tax | Tax-exempt organisations (calendar-year) | May 15, 2026 | November 16, 2026 (Form 8868) |
| 1041 | Income Tax Return for Estates and Trusts | Fiduciaries of estates and trusts | April 15, 2026 | September 30, 2026 (Form 7004) |
Payroll & information returns
| Form | Description | Who files | 2026 due date | Extended |
|---|---|---|---|---|
| W-2 / W-3 | Wage and Tax Statement | All employers | February 2, 2026 (recipients + SSA) | Form 8809, rarely granted |
| 1099-NEC | Nonemployee Compensation | Payers of $600+ to contractors | February 2, 2026 (recipients + IRS) | Form 8809, rarely granted |
| 1099-MISC | Miscellaneous Information | Rents, royalties, awards, other income | Mar 2 (paper) · Mar 31, 2026 (e-file) | Form 8809 |
| 941 | Employer's Quarterly Federal Tax Return | Employers withholding payroll taxes | Apr 30 · Jul 31 · Oct 31, 2026 · Feb 1, 2027 | No extension available |
| 940 | Employer's Annual Federal Unemployment (FUTA) Return | Employers subject to FUTA | February 2, 2026 | February 10 if all deposits made on time |
| 5500 | Annual Return/Report of Employee Benefit Plan | Plan sponsors (calendar-year plans) | July 31, 2026 | October 15, 2026 (Form 5558) |
Calendar
The 2026 compliance calendar at a glance
Deadlines that fall on a weekend or federal holiday shift to the next business day.
- Jan 15, 2026Q4 2025 individual estimated tax payment (1040-ES)
- Feb 2, 2026W-2s and 1099-NECs to recipients and the IRS/SSA; Form 940 due
- Mar 16, 2026Partnership (1065) and S corporation (1120-S) returns and K-1s
- Mar 31, 2026E-filing deadline for most information returns
- Apr 15, 2026Individual (1040), C corporation (1120), trust (1041), gift (709) returns; Q1 estimates
- May 15, 2026Exempt organisation returns (990 series)
- Jun 15, 2026Q2 estimated tax payment; returns for US citizens living abroad
- Jul 31, 2026Form 5500 for calendar-year benefit plans
- Sep 15, 2026Extended 1065 / 1120-S returns; Q3 estimated tax payment
- Oct 15, 2026Extended individual (1040) and C corporation (1120) returns
- Jan 15, 2027Q4 2026 individual estimated tax payment
Penalties
What missing a deadline actually costs
Penalty exposure is why capacity planning matters more than heroics in March and April.
Failure to pay
0.5% of unpaid tax per month, capped at 25%. An extension extends the filing date, never the payment date — estimate and pay by the original due date.
Late information returns
$60 – $340 per form depending on how late, with no cap for intentional disregard. W-2 and 1099-NEC deadlines are the most commonly missed.
FAQ
Common questions about US filing deadlines
What are the 2026 IRS filing deadlines for 1040, 1120 and 1065 returns?
For calendar-year filers in 2026: partnership (1065) and S corporation (1120-S) returns are due March 16, 2026 (March 15 falls on a Sunday); individual (1040), C corporation (1120) and trust (1041) returns are due April 15, 2026. Extensions push 1065 and 1120-S to September 15, 2026 and 1040 and 1120 to October 15, 2026.
Does a filing extension also extend the time to pay?
No. Forms 4868 and 7004 extend the filing deadline only. Any balance owed is still due on the original due date, and the failure-to-pay penalty of 0.5% per month plus interest starts accruing from that date.
Which forms does an outsourced tax preparation team typically handle?
Most CPA firms outsource preparation and workpaper build-out for 1040, 1040-NR, 1065, 1120, 1120-S, 1041 and 990 returns, plus 1099 and W-2 information return processing. Review and sign-off stay with the firm's licensed CPA — the offshore team prepares, reconciles and documents.
What happens if a partnership return is filed late?
The late-filing penalty for Forms 1065 and 1120-S is assessed per partner or shareholder per month (up to 12 months), so it scales quickly with the number of owners. First-time abatement or reasonable-cause relief may apply if the firm has a clean compliance history.
When are quarterly estimated tax payments due in 2026?
April 15, June 15 and September 15, 2026, with the fourth instalment due January 15, 2027. Corporations follow the 15th day of the 4th, 6th, 9th and 12th months of their tax year.
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