October 1

Trusts and estates: Filing an income tax return for the 2024 calendar year (Form 1041) and paying any tax, interest and penalties due, if an automatic five-and-a-half month extension was filed.

October 10

Individuals: Reporting September tip income, $20 or more, to employers (Form 4070).

October 15

Individuals: Filing a 2024 income tax return (Form 1040 or Form 1040-SR) and paying any tax, interest and penalties due, 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).

Individuals: Making contributions for 2024 to certain existing retirement plans or establishing and contributing to a SEP for 2024, if an automatic six-month extension was filed.

Individuals: Filing a 2024 gift tax return (Form 709) and paying any tax, interest and penalties due, if an automatic six-month extension was filed.

C corporations: Filing a 2024 income tax return (Form 1120) and paying any tax, interest and penalties due, if an automatic six-month extension was filed.

C corporations: Making contributions for 2024 to certain employer-sponsored retirement plans, if an automatic six-month extension was filed.

October 31

Employers: Reporting income tax withholding and FICA taxes for third quarter 2025 (Form 941) and paying any tax due.