Calendar-year corporations: Pay the third installment of 2025 estimated income taxes and complete Form 1120-W for the corporation’s records.

Calendar-year partnerships: File a 2024 income tax return (Form 1065 or Form 1065-B) and provide each partner with a copy of Schedule K-1 (Form 1065) or a substitute Schedule K-1 if an automatic six-month extension was filed.

Calendar-year S corporations: File a 2024 income tax return (Form 1120-S) and provide each shareholder with a copy of Schedule K-1 (Form 1120-S) 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 2024 to certain employer-sponsored retirement plans 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.

Individuals: Pay the third installment of 2025 estimated taxes (Form 1040-ES), if not paying income tax through withholding or not paying sufficient income tax through withholding.