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LEARNING CENTER

Key Tax Deadlines for Businesses in September 2025

As September approaches, it brings with it a range of crucial tax deadlines for businesses. Understanding and adhering to these deadlines is essential for ensuring compliance and optimizing your financial management. Below is a detailed overview of the key tax obligations for various business structures during September 2025.

September 15 - S Corporations
For S corporations, September 15 is the deadline to file the income tax return for the 2024 calendar year, specifically the Form 1120-S, and pay any taxes due. This applies only if an automatic six-month extension was previously requested. Additionally, each shareholder should receive a Schedule K-1 (Form 1120-S), or substitute Schedule K-1, and if necessary, a Schedule K-3 (Form 1120-S) or substitute Schedule K-3 to ensure transparency and compliance with tax obligations.

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September 15 - Corporations
On this same date, corporations are also required to deposit their third installment of estimated tax for the 2025 calendar year. This installment is a critical part of managing corporate tax liabilities and avoiding unnecessary penalties.

September 15 - Partnerships
Partnerships must submit the Form 1065 tax return for the 2024 calendar year, assuming a six-month extension was granted. Each partner should receive their respective Schedule K-1 (Form 1065), or substitute Schedule K-1, and if required, a Schedule K-3 (Form 1065) or substitute Schedule K-3 to accurately report earnings within the partnership.

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September 15 - Social Security, Medicare, and Withheld Income Tax
Employers who follow the monthly deposit rules must make deposits for Social Security, Medicare, and withheld income tax by September 15 for the month of August 2025. The same deadline applies to nonpayroll withholding deposits under the monthly rule.

Consideration for Weekends & Holidays:

If any tax deadline falls on a weekend or a legal holiday, it is automatically extended to the next business day. This extension can provide a strategic advantage in managing last-minute filings.

Extensions for Disaster Areas:
In areas declared as disaster zones, there may be extensions available for tax filing dates. To verify if your region qualifies and for the latest information, visit the FEMA and IRS websites.

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