Not tax advice. Computation tools only. Have a professional review before filing.

tax-calendar/us/us-q3-estimated-tax-september-15

USSelf-employedSmall business

Q3 Estimated Tax (Form 1040-ES)

Third-quarter federal estimated tax payment for US self-employed individuals. Covers income earned June 1 through August 31, 2026.

Filing deadline

September 15, 2026

Country: United States
Tax year: 2025
Official: Tax authority

What is this deadline?

Q3 estimated tax payment. Covers June, July, and August 2026 earnings.

Who needs to file?

Same as Q1 and Q2 — anyone with non-withheld income expecting $1,000+ in tax owed.

How to file

IRS Direct Pay, EFTPS, or mail Form 1040-ES.

What people miss

By this point in the year you have 8 months of actual income data. Re-run your full-year projection and adjust Q3/Q4 payments accordingly. Overpaying Q1/Q2 then underpaying Q3/Q4 triggers annualised-income-installment penalties unless you file Form 2210 Schedule AI.

Prepare this return with open-source skills

These skills are in the OpenAccountants repo. Clone them into Claude, Cursor, or any AI agent and they handle the computation.

us-quarterly-estimated-tax.mdUS

Use this skill whenever asked about US federal quarterly estimated income tax payments for sole proprietors and single-member LLCs. Trigger on phrases like "1040-ES", "estimated tax", "quarterly tax", "safe harbor", "underpayment penalty", "Form 2210", "annualized income", or any question about federal estimated tax requirements. Covers the $1,000 threshold, 100%/110% prior-year safe harbor, 90% current-year method, quarterly due dates, annualized income instalment method, Form 2210 penalty computation, and withholding strategies. MUST be loaded alongside us-tax-workflow-base v0.1+. Federal only.

This page is informational only and not tax advice. Verify dates and requirements against the official tax authority before filing.

Q2 Estimated Tax (Form 1040-ES)

Extended Federal 1040 Deadline

All United States deadlines Global calendar