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Important September 2025 Tax Deadlines for Businesses

As September 2025 approaches, it's crucial for businesses to keep track of key tax deadlines. This includes submissions for S corporations, partnerships, and critical employer-related deposits due by September 15.

September 15 - S Corporations
It's deadline time for filing the 2024 calendar year income tax return (Form 1120-S) with payment for any tax due, provided an automatic 6-month extension was granted. Ensure each shareholder receives their Schedule K-1 (Form 1120-S) or a substitute. Don’t overlook Schedule K-3 (Form 1120-S) if required.

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September 15 - Corporations
For calendar year corporations, the third installment of estimated income tax for 2025 is due. Plan ahead to manage your corporate cash flow effectively.

September 15 - Partnerships
If you're operating as a partnership, file your 2024 return using Form 1065 if you've been granted a 6-month extension. Distribute Schedule K-1 (Form 1065) or its substitute to each partner, along with Schedule K-3 if applicable.

September 15 - Social Security, Medicare and Withheld Income Tax
Employers, take note: under the monthly deposit rules, deposits for Social Security, Medicare, and withheld income tax for August 2025 are due. Nonpayroll withholding must also be taken care of by this date, if relevant.

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Handling Weekends & Holidays
Should any due date fall on a weekend or legal holiday, it will be extended to the next working day.

Disaster Area Extensions
If you're based in a disaster area, postponements for due dates may be in place. For updates and clarification, check current status via FEMA: https://www.fema.gov/disaster/declarations and IRS: https://www.irs.gov/newsroom/tax-relief-in-disaster-situations.

Businesses should ensure all filings and payments are made on time to avoid penalties and maintain compliance. Stay informed and organized to make the most of your fiscal strategy.

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