Upcoming Tax Due Dates

September 15

Individuals

- Pay the third installment of 2026 estimated taxes (Form 1040-ES), if not paying income tax through withholding or not paying sufficient income tax through withholding.

Calendar-year corporations

- Pay the third installment of 2026 estimated income taxes, completing Form 1120-W for the corporation’s records.

Calendar-year S corporations

- File a 2025 income tax return (Form 1120-S) and provide each shareholder with a copy of Schedule K-1 (Form 1120S) or a substitute Schedule K-1 if an automatic six-month extension was filed. Pay any tax, interest and penalties due.

Calendar-year S corporations

- Make contributions for 2025 to certain employer-sponsored retirement plans if an automatic six-month extension was filed.

Calendar-year partnerships

- File a 2025 income tax return (Form 1065 or Form 1065-B) and provide each partner with a copy of Schedule K1 (Form 1065) or a substitute Schedule K1 if an automatic six-month extension was filed.

Employers

- Deposit Social Security, Medicare and withheld income taxes for August if the monthly deposit rule applies.

Employers

- Deposit nonpayroll withheld income tax for August if the monthly deposit rule applies.

September 30

Calendar-year trusts and estates

- File a 2025 income tax return (Form 1041) if anautomatic five-and-a-half-month extension was filed. Pay any tax, interest and penalties due.

October 13

Individuals

- Report September tip income of $20 or more to employers (Form 4070).