09/10/2026
Upcoming Sept. 15 Tax Deadlines
Sept. 15 brings several important federal tax deadlines. Reviewing affected clients now can help prevent missed filings and payments, not to mention potential penalties.
Key deadlines include:
Estimated taxes: Third-quarter 2026 estimated tax payments are due for individuals and corporations, including self-employed taxpayers and others who may not have enough tax withheld.
Partnership returns: Calendar-year partnerships that received a six-month extension must file Form 1065, U.S. Return of Partnership Income.
S corporation returns: Calendar-year S corporations with valid six-month extensions must file Form 1120-S, U.S. Income Tax Return for an S Corporation.
Payroll taxes: Employers that follow the monthly deposit rule must deposit Social Security, Medicare and withheld federal income taxes for payments made in August.