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Key September 2025 Tax Deadlines for Business Owners

As a savvy business owner, staying on top of your tax responsibilities is crucial to maintaining financial clarity and avoiding unnecessary penalties. With September 2025 approaching, now is the time to ensure you’re prepared to meet critical tax deadlines. Below, we break down essential due dates for S corporations, partnerships, and employers, so you can focus on what truly matters—growing your business.

September 15 - S Corporations
Mark your calendar: September 15 is the deadline for filing your 2024 calendar year income tax return (Form 1120-S) if you requested an automatic 6-month extension. Don’t forget to distribute each shareholder’s Schedule K-1 (or substitute) and, if pertinent, the Schedule K-3 (or substitute) to ensure they’re well-acquainted with their profit distribution details. Staying organized can make all the difference during tax season.

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September 15 - Corporations
If your corporation follows a calendar year, be ready to deposit the third installment of your estimated income tax for 2025 by this date. Consistent payments can streamline your end-of-year financial reporting and mitigate unexpected cash outflows.

September 15 - Partnerships
For partnerships that filed an extension, September 15 is your deadline to submit the 2024 calendar year return (Form 1065). Don’t overlook providing each of your partners with their Schedule K-1 and, when necessary, their Schedule K-3. Timely communication helps maintain transparency and trust among partners.

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September 15 - Social Security, Medicare, and Withheld Income Tax
This date also marks the deadline for employers adhering to monthly deposit rules to submit Social Security, Medicare, and withheld income taxes for August 2025. The same applies to nonpayroll withholding deposits. Adhering to these schedules not only keeps you compliant but safeguards your business reputation.

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Weekends & Holidays:
If any deadline falls on a weekend or federal holiday, your due date will be extended to the next business day not recognized as a holiday, giving you some breathing room.

Disaster Area Extensions:
When areas are hit by disasters, filing deadlines may be extended. To check whether your area qualifies, visit these resources:
FEMA: https://www.fema.gov/disaster/declarations
IRS: https://www.irs.gov/newsroom/tax-relief-in-disaster-situations

At ChesebroCPA, we understand the dynamic challenges small business owners face, particularly in the high-demand construction industry. Our mission is to minimize your tax-related stress and maximize your financial insights. Reach out to us for tailored advice and let our expert team guide you through the complex world of tax compliance.

Schedule a Complimentary Meeting
Learn how we can help serve your business needs.
Schedule Here
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