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Key Tax Deadlines for September 2025: What to Know

As we enter the fall of 2025, staying informed about critical tax due dates is essential for individuals managing their finances and tax obligations. This month, key deadlines include tip reporting and estimated tax payments. We'll explore safe harbor rules to help you avoid penalties and strategies to prepare your finances for 2026.

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2025 Fall & 2026 Tax Planning

Engage with our office to schedule a tax planning consultation that ensures you are ready for upcoming requirements and opportunities.

September 10 - Tip Reporting Deadline

Employees who receive tips must report any amount over $20 earned in August to their employers by September 10 using IRS Form 4070. Your employer will withhold the appropriate FICA and income taxes from your regular wages. If your earnings don’t cover these withholdings, note that this will reflect in box 8 of your W-2, and you must reconcile this when filing your annual return.

September 15 - Estimated Tax Payment Due

The third installment for 2025 individual estimated taxes is due. As participants in a "pay-as-you-earn" system, various methods help taxpayers comply with required payments, including:

  • Payroll withholding for employees
  • Pension withholding for retirees
  • Estimated tax payments for self-employed individuals and those with additional income not covered by withholding

Failing to prepay a minimum safe harbor amount can incur an underpayment penalty, calculated as the federal short-term rate plus 3%. Tax law, however, provides ways to avoid this through safe harbor prepayments:

  • Current Year Safe Harbor: Pay at least 90% of your current tax year’s liability.
  • Prior Year Safe Harbor: For those with an AGI above $150,000 ($75,000 if married and filing separately), 110% of the previous year’s tax applies; otherwise, it is 100%.

Example: If your total tax for the year amounts to $10,000 and you've prepaid $5,600, owing an additional $4,400 is expected. While you miss the first safe harbor, if your previous year's tax was $5,000, prepaying $5,600 exceeds the 110% threshold, thus qualifying you for this safe harbor, averting the penalty.

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Notice: State rules for de minimis amounts and safe harbor estimates may vary from federal regulations. Contact our office for state-specific advice.

Key Extensions and Exceptions

If a tax due date lands on a weekend or legal holiday, it automatically advances to the next business day. Additionally, areas declared as disaster zones receive further extensions. Verify affected areas and corresponding extensions on the following websites:

It’s critical to understand these rules to make strategic tax payments, avoiding unexpected penalties, and optimizing your financial standing. For personalized guidance, don’t hesitate to reach out for a consultation.

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