September 2026 Individual Due Dates & Estimated Taxes

Fall is an excellent time to review your 2026 tax situation and get a head start on 2027. With a major estimated tax deadline arriving this month, now is the perfect moment to check your income, withholding, and estimated payments. Making adjustments before year-end can save you from unexpected tax bills or penalties later.

September 10: Report August Tips to Your Employer

If you work for tips and earned more than $20 during August, you must report that income to your employer by September 10. You can use IRS Form 4070 or simply provide a signed statement. Be sure to include your signature, name, address, Social Security number, your employer's name and address (or the establishment's name), the specific period covered, and the total tips received.

Once reported, your employer is required to withhold income and FICA taxes from your regular wages to cover those tips. If your regular paycheck isn't large enough to cover the withholding, your employer will report the uncollected amount in box 8 of your W-2. You will then need to pay that uncollected withholding when you file your annual tax return.

September 15: Third Quarter Estimated Tax Payment

Business owner reviewing financial documents

The third installment of your 2026 individual estimated taxes is due on September 15. The U.S. operates on a "pay-as-you-earn" tax system, meaning you are expected to pay taxes as you generate income throughout the year.

The government offers a few ways to help taxpayers meet this requirement:

  • Payroll withholding for employees

  • Pension withholding for retirees

  • Estimated tax payments for self-employed individuals and those with other income sources not covered by withholding

Avoiding the Underpayment Penalty

If you fall short of a minimum required prepayment (known as a safe harbor), you may face an underpayment penalty. This penalty is calculated quarter-by-quarter and equals the federal short-term rate plus 3 percentage points.

Fortunately, federal tax law provides ways to avoid this penalty. First, if your underpayment is less than $1,000 (the de minimis amount), no penalty is assessed. Otherwise, you can rely on one of these two safe harbor rules:

  • Current Year Safe Harbor: You will avoid a penalty if your payments equal or exceed 90% of the tax you owe in the current year.

  • Prior Year Safe Harbor: You can also avoid a penalty by paying 100% of your prior year's tax liability. However, if your Adjusted Gross Income (AGI) exceeds $150,000 (or $75,000 if married filing separately), this safe harbor jumps to 110% of your prior year's tax.

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How the Safe Harbor Works in Practice

Let's look at a quick example. Suppose your total tax for the current year will be $10,000, and your prepayments add up to $5,600. That leaves you owing an additional $4,400. Do you owe a penalty?

First, check the 90% rule. Since 90% of $10,000 is $9,000, your $5,600 in prepayments falls short. You can't avoid the penalty under this exception.

But let's assume your tax liability for the prior year was $5,000. Because you prepaid $5,600—which is greater than 110% of your prior year's tax ($5,500)—you successfully meet the second safe harbor and escape the penalty entirely.

This highlights why keeping an eye on your prepayments is so vital, especially if you experience a large increase in income from selling property, realizing large stock gains, earning big bonuses, or retiring. You must also make each installment payment on time to qualify for the safe harbor exceptions.

Caution: Some state rules regarding de minimis amounts, safe harbor calculations, and due dates differ from federal guidelines. Check with us for the specific safe harbor rules in your state.

Weekend and Holiday Rule

If any tax due date falls on a Saturday, Sunday, or legal holiday, your deadline is automatically extended to the next business day that is not a legal holiday.

Disaster Area Extensions

When a geographical area is federally designated as a disaster area, tax due dates are extended to provide relief. To check if your location qualifies for an extension, you can visit these official resources:

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

We Are Here to Help

Keeping up with estimated taxes and safe harbor rules can feel overwhelming, especially when you are managing a small business or an unexpected increase in income.

If this sounds familiar, we can walk you through it step by step. Contact our office today to schedule a tax planning consultation and ensure you are safely on track before year-end.

Virtual AI
If you’re ready to get a handle on your tax situation, reach out and we’ll guide you through each step.
Let’s Sort This Out
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