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

Calendar-year trusts and estates - File a 2023 income tax return (Form 1041) if an automatic five-and-a-half-month extension was filed. Pay any tax, interest and penalties due.

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

Individuals - File a 2023 income tax return (Form 1040 or Form 1040-SR) if an automatic six-month extension was filed (or if an automatic four-month extension was filed by a taxpayer living outside the United States and Puerto Rico). Pay any tax, interest and penalties due.

Individuals - Make contributions for 2023 to certain existing retirement plans or establish and contribute to a SEP for 2023 if an automatic six-month extension was filed.

Individuals - File a 2023 gift tax return (Form 709) and pay any tax, interest and penalties due if an automatic six-month extension was filed.

Calendar-year bankruptcy estates - File a 2023 income tax return (Form 1041) if an automatic six-month extension was filed. Pay any tax, interest and penalties due.

Calendar-year C corporations - File a 2023 income tax return (Form 1120) if an automatic six-month extension was filed. Pay any tax, interest and penalties due.

Calendar-year C corporations - Make contributions for 2023 to certain employer-sponsored retirement plans if an automatic six-month extension was filed.

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

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