Key Tax Deadlines for September 2025

As we approach September 2025, it's essential to understand the crucial tax deadlines, including tip reporting and estimated tax payments. This guide will delve into safe harbor regulations, strategies to avoid penalties, and preparation methods for the 2026 tax year.

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Fall 2025 and Planning for 2026

Reach out to our office to book a consultation for tax planning as we transition into fall 2025.

September 10 - Tip Reporting

Employees receiving tips exceeding $20 in August must report them using IRS Form 4070 by September 10. Employers are obligated to withhold FICA and income taxes from these tips. If regular wages don't cover these obligations, the uncollected amounts will be indicated in box 8 of your W-2. You'll need to settle this when filing your annual return.

September 15 - Estimated Tax Payment

The third quarter of estimated tax payments for individuals is due on September 15. The federal tax system operates on a "pay-as-you-earn" basis, supported by mechanisms like:

  • Payroll withholding for employees.
  • Pension withholding for retirees.
  • Estimated payments for self-employed individuals and others without withholding options.
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Understanding Penalties and Safe Harbors

Failure to prepay the required amount may result in an underpayment penalty, calculated as the federal short-term rate plus 3 percentage points, assessed quarterly.

To evade this penalty, aim to meet one of the following safe harbors:

  • Prepay 90% of this year's total tax liability.
  • Match 100% of last year’s tax liability, with an adjustment to 110% if your AGI exceeds $150,000 (or $75,000 for separate filers).

For example, if your annual tax is $10,000 and prepayments are $5,600, you owe $4,400. While you don't meet the 90% rule (needing $9,000), you do qualify under the prior year rule if your previous tax was $5,000, as you prepaid $5,600.

Be mindful of income spikes from stocks, property sales, significant bonuses, or retirement, and ensure estimated payments align with these changes.

State Variations and Considerations

Note that state-level de minimis and safe harbor rules may differ from federal standards. Contact our office for state-specific guidance.

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Adjustments for Weekends, Holidays, and Disasters

If a deadline falls on a weekend or holiday, it extends to the next business day. Additionally, disaster areas receive filing extensions; verify these via FEMA and IRS resources:

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