Sole Proprietorship Tax Due Dates and Penalties

A sole proprietor’s federal tax year runs on the same April 15 deadline as any individual return, but that single date is only one of several sole proprietorship tax deadlines to keep straight. Quarterly estimated payments come due four times a year, Form 1099-NEC for contractors is due at the end of January, and each missed date carries its own penalty. The full 2026 calendar sits at the bottom of this page.

The April 15 Annual Return

Your federal income tax return is due April 15 following the close of the calendar year. For the 2025 tax year, that means April 15, 2026.¹ When April 15 lands on a weekend or federal holiday, the deadline shifts to the next business day. A sole proprietorship isn’t a separate legal entity, so all business income and expenses go on your personal Form 1040 with Schedule C attached to show your business profit or loss.²

State returns for most income-tax states share the April 15 date, but confirm yours with the state tax agency because a handful set different deadlines and some states have no income tax at all.

Filing an Extension

If you can’t finish the return in time, file Form 4868 by April 15 and you get an automatic six-month extension to October 15.³ The extension is free and requires no reason.

The catch: an extension to file is not an extension to pay.⁴ Any tax you owe is still due April 15. When you submit Form 4868, estimate your liability and pay it with the extension request. Otherwise interest and late-payment penalties start accruing on the unpaid balance the next day.

Quarterly Estimated Tax Payments

Federal tax is pay-as-you-go. Employees have it withheld from each paycheck; sole proprietors send it in themselves through quarterly estimated payments. You generally have to make these payments if you expect to owe $1,000 or more in federal tax for the year after subtracting withholding and refundable credits.⁵

The four due dates for tax year 2026 are:

1st quarter: April 15, 2026
2nd quarter: June 15, 2026
3rd quarter: September 15, 2026
4th quarter: January 15, 2027

The quarters aren’t evenly spaced. Two months separate the first and second payments; three months separate the second and third. Missing any of these dates triggers an underpayment penalty on that specific installment, even if you square up your full annual liability when you file.⁶

Safe Harbors That Avoid the Penalty

The IRS won’t charge an underpayment penalty if your estimated payments plus any withholding meet one of two thresholds:

Current-year test: you paid at least 90% of the tax you owe for 2026.
Prior-year test: you paid at least 100% of your total 2025 tax liability. If your 2025 adjusted gross income exceeded $150,000 ($75,000 if married filing separately), the threshold rises to 110%.

You only need to meet one.⁶ The prior-year test is useful for sole proprietors with unpredictable income because it gives you a fixed target based on last year’s numbers rather than a guess at this year’s profits. The worksheets in Form 1040-ES walk through calculating each installment.⁷

Self-Employment Tax Rolls Into the Same Dates

On top of income tax, sole proprietors owe self-employment tax for Social Security and Medicare. The combined rate is 15.3%: 12.4% for Social Security and 2.9% for Medicare.⁸ That’s effectively double what a W-2 employee sees, because you’re covering both the employer and employee halves.

You owe self-employment tax once your net earnings from self-employment reach $400 for the year. Report it on Schedule SE, attached to Form 1040 alongside Schedule C.⁹ The Social Security portion applies only to the first $184,500 in net earnings for 2026; earnings above that are subject to just the 2.9% Medicare tax.¹⁰ Half of your self-employment tax is deductible when calculating adjusted gross income, and that deduction goes on Form 1040, not Schedule C.¹¹

Fold self-employment tax into your quarterly estimated payments along with income tax. The underpayment penalty applies to the combined amount, not just the income tax side.

January 31 for Contractor 1099s

If your business paid $600 or more to an independent contractor, freelancer, or other nonemployee during the year, you must file Form 1099-NEC for that payment. Both the copy furnished to the recipient and the copy filed with the IRS are due January 31 of the following year.¹² That makes it the earliest federal tax deadline of the year. If you file 10 or more information returns of any type combined, you must file them electronically.¹³

Penalties for Missing Each Deadline

The IRS treats late filing and late payment as two separate problems, each with its own penalty, and they can stack.

Failure-to-File

Filing after April 15 (or after October 15 with an extension) costs 5% of your unpaid tax per month or partial month, capped at 25%.¹⁴ That cap hits after five months. On a $10,000 balance, filing six months late means $2,500 in failure-to-file penalty on top of the tax itself.

Failure-to-Pay

Filing on time but not paying the full balance costs 0.5% of the unpaid tax per month, also capped at 25%.¹⁵ That slower rate takes 50 months to reach the cap, and it drops to 0.25% per month once you’re on an approved installment agreement. Interest accrues on top at the IRS underpayment rate, currently in the 6% to 7% annual range depending on the quarter.¹⁶

When both penalties apply in the same month, the failure-to-file penalty is reduced by the failure-to-pay amount, so the combined rate during the first five months is 5% per month rather than 5.5%.¹⁷ The practical rule: file on time even if you can’t pay. Filing eliminates the steeper penalty and buys room to work out the balance.

Estimated Tax Underpayment

Missing a quarterly payment triggers a separate penalty, calculated by applying the IRS underpayment interest rate to each late or short installment for the period it stayed unpaid.⁶ The penalty is assessed per quarter, so a late first-quarter payment generates a penalty even if you overpay in the second. Meeting one of the safe harbors described above is the cleanest way to avoid it.

Full 2026 Federal Deadline Calendar

January 15, 2026: Fourth quarter 2025 estimated payment
January 31, 2026: File Form 1099-NEC for 2025 contractor payments
April 15, 2026: File 2025 Form 1040 with Schedule C and Schedule SE (or file Form 4868 for an extension); pay any remaining 2025 balance; first quarter 2026 estimated payment
June 15, 2026: Second quarter 2026 estimated payment
September 15, 2026: Third quarter 2026 estimated payment
October 15, 2026: File 2025 Form 1040 if you requested an extension
January 15, 2027: Fourth quarter 2026 estimated payment

Any date that falls on a weekend or federal holiday moves to the next business day.¹

1
Internal Revenue Service. When to File
2
Internal Revenue Service. About Schedule C (Form 1040), Profit or Loss from Business (Sole Proprietorship)
3
Internal Revenue Service. Form 4868, Application for Automatic Extension of Time To File U.S. Individual Income Tax Return
4
Internal Revenue Service. IRS Reminds Taxpayers an Extension to File Is Not an Extension to Pay Taxes
5
Internal Revenue Service. Form 1040-ES, Estimated Tax for Individuals
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Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual to Pay Estimated Income Tax
7
Internal Revenue Service. About Form 1040-ES, Estimated Tax for Individuals
8
Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes)
9
Internal Revenue Service. About Schedule SE (Form 1040), Self-Employment Tax
10
Social Security Administration. Contribution and Benefit Base
11
Social Security Administration. If You Are Self-Employed
12
Internal Revenue Service. Instructions for Forms 1099-MISC and 1099-NEC
13
Internal Revenue Service. Reporting Payments to Independent Contractors
14
Internal Revenue Service. Failure to File Penalty
15
Internal Revenue Service. Failure to Pay Penalty
16
Internal Revenue Service. Quarterly Interest Rates
17
Internal Revenue Service. Topic No. 653, IRS Notices and Bills, Penalties and Interest Charges