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Key Individual Tax Deadlines and Obligations for September 2026

Fall is an excellent time to evaluate your 2026 tax situation and begin strategizing for 2027. With a major estimated tax payment due this month, it is an ideal opportunity to review your income, withholdings, and estimated payments to determine if any adjustments are necessary before the year ends.

September 10: Deadline to Report August Tips

If you work for tips and received more than $20 during the month of August, you are required to report this income to your employer no later than September 10. You can use IRS Form 4070 or provide a signed statement that includes your name, address, Social Security number, employer's name (and establishment name if different), the period covered, and the total tips received.

Your employer uses this report to withhold FICA and income taxes from your regular wages. If your standard wages do not cover the required withholding, the uncollected amount will be reported in Box 8 of your W-2. You will then be responsible for paying this uncollected withholding when filing your annual tax return.

September 15: Third Quarter Estimated Tax Payment

The third installment for 2026 individual estimated taxes is due on September 15. The federal tax system operates on a "pay-as-you-earn" basis, meaning taxes must be paid as income is earned or received during the year. This requirement is typically met through:

  • Payroll withholding for employees;
  • Pension withholding for retirees; and
  • Estimated tax payments for self-employed individuals and those with income sources not subject to withholding.
Tax planning and estimated payments

Understanding Underpayment Penalties and Safe Harbors

Falling short on your minimum prepayments can result in an underpayment penalty. Calculated quarterly, this penalty equals the federal short-term rate plus 3 percentage points.

However, the tax code provides ways to avoid this penalty. First, if your underpayment is less than $1,000 (the de minimis amount), no penalty is assessed. Beyond that, the IRS offers two primary "safe harbor" prepayments:

  • Current Year Safe Harbor: You avoid penalties if your total payments equal or exceed 90% of the tax owed for the current year.
  • Prior Year Safe Harbor: You are protected if you pay 100% of your tax liability from the immediately preceding year. For taxpayers with an Adjusted Gross Income (AGI) over $150,000 (or $75,000 for married couples filing separately), this threshold increases to 110% of the prior year's tax.

Safe Harbor Example

Suppose your total tax for the year is $10,000, and your prepayments total $5,600. This leaves a balance of $4,400. To see if the first safe harbor applies, calculate 90% of $10,000, which is $9,000. Since your $5,600 prepayment falls short, this exception does not apply.

However, assume your tax for the prior year was $5,000. Since your $5,600 prepayment is greater than 110% of the prior year's tax ($5,500), you qualify for the second safe harbor and successfully avoid the penalty.

This highlights the importance of monitoring prepayments, especially following a significant income increase from events like stock or property sales, large bonuses, or retirement distributions. Timely payment of each required installment is necessary to qualify for these safe harbors.

Caution: State-level rules for de minimis amounts, safe harbors, and estimated payment due dates may differ from federal guidelines. Please contact our office to discuss your specific state rules.

Adjustments for Weekends and Legal Holidays

When a tax due date falls on a Saturday, Sunday, or legal holiday, the deadline is automatically pushed to the next business day that is not itself a legal holiday.

Deadline Extensions for Designated Disaster Areas

If you live or operate a business in a federally designated disaster area, due dates are typically extended to provide relief. To check if your geographical area qualifies for an extension, visit the following resources:

FEMA: https://www.fema.gov/disaster/declarations
IRS: https://www.irs.gov/newsroom/tax-relief-in-disaster-situations

Navigate Your September Tax Requirements with Confidence

Staying proactive with estimated payments and reporting requirements during the fall sets a strong foundation for your year-end tax planning. Managing safe harbor calculations can be complex, particularly if you have experienced notable changes to your income this year.

Contact this office today to schedule a tax planning consultation. We can review your income, withholding, and estimated payments to ensure your strategy is optimized and penalty-free before the year closes.

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