09/01/2026
The third 2026 estimated tax payment is due September 15. Learn who should pay, safe harbor rules, penalties, and how to avoid a surprise tax bill.
If you make or receive income that is not fully covered by withholding, September 15, 2026 is an important date on the tax calendar. It is the due date for the third installment of 2026 federal estimated tax payments for individuals who are not paying enough through withholding during the year.