September 2026 Individual Tax Deadlines and Planning Guide

As we transition into fall, it is an excellent time to evaluate your 2026 tax situation and begin looking ahead to 2027. With a major estimated tax payment due this month, September offers a natural checkpoint to review your income, withholdings, and estimated payments. Making necessary adjustments now can help you avoid surprises and penalties at year-end. If you are unsure where you stand, reach out to our office to schedule a personalized tax planning consultation.

Tax professional helping a client

September 10: Reporting August Tips to Your Employer

If you are an employee who works for tips and accumulated more than $20 in tip income during the month of August, you must report this to your employer no later than September 10. You can submit this report using IRS Form 4070 or by providing your own signed written statement.

If you choose to write your own statement, it must include your name, address, Social Security number, the name and address of your employer (or the establishment), the specific month or period covered, and the total tips received during that timeframe.

Once reported, your employer is required to calculate and withhold FICA and income taxes on these tips from your regular wages. If your standard wages are not sufficient to cover the necessary FICA and tax withholding, the uncollected amount will be reported in box 8 of your annual W-2. You will then be responsible for paying that uncollected withholding when you file your tax return for the year.

September 15: Q3 Estimated Tax Payments Due

The third installment for 2026 individual estimated taxes is due on September 15. Because the federal tax system operates on a "pay-as-you-earn" basis, the government provides several ways to help taxpayers pay tax on income as it is earned. These methods include:

  • Payroll withholding for employees;

  • Pension withholding for retirees; and

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

Failing to prepay a minimum required amount (known as a safe harbor) can trigger an underpayment penalty. This penalty is calculated on a quarter-by-quarter basis and is equal to the federal short-term rate plus 3 percentage points.

Small business owner reviewing records

Avoiding Penalties with Safe Harbor Rules

Federal tax law offers specific safe harbor provisions to help you avoid the underpayment penalty. First, if your total underpayment is less than $1,000 (the de minimis amount), no penalty is assessed. Beyond that, there are two primary safe harbor prepayments:

  • The Current Year Safe Harbor: If your payments equal or exceed 90% of the tax owed for the current year, you will escape the penalty.

  • The Prior Year Safe Harbor: You can also avoid the penalty if your prepayments equal 100% of your prior year's tax liability. However, for taxpayers whose Adjusted Gross Income (AGI) exceeds $150,000 (or $75,000 for married taxpayers filing separately), this safe harbor threshold increases to 110% of the prior year's tax.

Let’s Start a Conversation.
You can count on us for professional guidance along with timely, and reliable tax services. If you’re ready to get started, or just want to start a conversation, then click below.
Learn More

Example: Suppose your tax for the year is $10,000, but your prepayments total just $5,600, leaving you with an additional $4,400 owed on your return. To test the first safe harbor exception, we calculate 90% of $10,000, which is $9,000. Since your $5,600 prepayment falls short, this exception does not apply.

However, let's assume your tax liability for the prior year was $5,000. Under the second safe harbor rule, you need to have paid in 110% of that prior year amount (110% of $5,000 is $5,500). Because your $5,600 prepayment exceeds the $5,500 requirement, you successfully meet this safe harbor and can escape the penalty.

This example highlights why monitoring your prepayments is essential, particularly if you experience a significant increase in income from large bonuses, retirement, or a large gain from the sale of stocks or property. Keep in mind that making each required estimated tax installment on time is also necessary to qualify for the safe harbor exception.

CAUTION: Many states have different rules for de minimis amounts, safe harbor estimates, and exact due dates. Please call our office to discuss the specific state safe harbor rules that apply to you.

Weekend, Holiday, and Disaster Area Extensions

While timing is generally strict, certain automatic extensions apply to deadlines. If a tax due date falls on a Saturday, Sunday, or legal holiday, the deadline automatically shifts to the next business day that is not a legal holiday.

Furthermore, due dates are extended for taxpayers located in geographically designated disaster areas. To verify if your location qualifies as a disaster area and to find specific filing extension dates, visit the following official resources:

Review Your Tax Strategy Before Year-End

September deadlines provide a crucial checkpoint to ensure you are on track with your tax obligations before the year closes. Whether you need to adjust your estimated payments, clarify state-specific rules, or discuss a sudden change in income, proactive planning is the best strategy. Contact our office today to schedule a comprehensive tax planning consultation.

Let’s Start a Conversation.
You can count on us for professional guidance along with timely, and reliable tax services. If you’re ready to get started, or just want to start a conversation, then click below.
Learn More
Share this article...

Want tax & accounting tips and insights?

Sign up for our newsletter.

I confirm this is a service inquiry and not an advertising message or solicitation. By clicking “Submit”, I acknowledge and agree to the creation of an account and to the and .
Let Wastvedt and Company, Inc. remove your tax & accounting stress today.
Contact us to learn more.
Wastvedt and Company, Inc. We love to chat!
Please feel free to use the contact button or use our Ai powered chat assistant.
Please fill out the form and our team will get back to you shortly The form was sent successfully