September 2026 Individual Tax Deadlines: Estimated Payments and Safe Harbors

Name: Christiansen Accounting
Address: 140 W Foothill Blvd Ste E, Claremont, California, 91711
Telephone: (909) 447-6802

Fall is an excellent time to evaluate your 2026 tax situation and lay the groundwork for 2027. With an estimated tax payment due this month, now is the perfect opportunity to review your income, withholding, and estimated payments to see if you need to make any adjustments before the year ends.

September 10: Reporting August Tips

If you are an employee who works for tips and you received more than $20 in tips during the month of August, you are required to report that income to your employer no later than September 10. You can submit this report using IRS Form 4070 or by providing a signed statement. Your statement must include your name, address, and Social Security number; your employer's name and address (or the establishment's name); the specific month or period the report covers; and the total tips you received during that time.

Once reported, your employer is required to withhold FICA and income taxes for these tips directly from your regular wages. If your regular paycheck is not large enough to cover the required FICA and tax withholding, your employer will report the uncollected amount in box 8 of your W-2. You will then be responsible for paying that uncollected withholding when you file your tax return for the year.

September 15: Third Quarter Estimated Taxes

The third installment of 2026 individual estimated taxes is due on September 15. The U.S. tax system operates on a "pay-as-you-earn" basis, meaning the government expects to collect taxes as you generate income. To help taxpayers meet this ongoing requirement, there are several collection methods in place:

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

How to Avoid Underpayment Penalties

If you fail to prepay a minimum required amount throughout the year, you can be hit with an underpayment penalty. This penalty is calculated quarter-by-quarter and is equal to 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. Beyond that, the IRS offers two primary "safe harbor" prepayments:

The Current Year Safe Harbor: If your total payments equal or exceed 90% of the tax you owe in the current year, you escape the penalty.
The Prior Year Safe Harbor: Alternatively, you can base your prepayments on what you owed the previous year. This safe harbor is generally met if you pay 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), the prior year safe harbor requirement jumps to 110%.

A Safe Harbor Example

Suppose your total tax for the year is $10,000, and your prepayments total $5,600. This leaves you owing an additional $4,400 on your tax return. To see if you owe a penalty, we first check the current year exception. Since 90% of $10,000 is $9,000, your $5,600 in prepayments falls short. You cannot avoid the penalty under the first safe harbor.

However, the second safe harbor may still protect you. 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 qualify for this safe harbor and avoid the penalty entirely.

This example highlights how important it is to ensure your prepayments are sufficient, especially if you experience a large jump in income. Sudden income increases are common when you sell stock or property, receive a large bonus, or retire. Remember that you must also make each required estimated tax installment on time to rely on these safe harbor exceptions.

CAUTION: State tax authorities, including the state of California, often have different de minimis amounts, alternative safe harbor rules, and separate due dates for estimated payments. Please reach out to our office to verify the specific safe harbor rules that apply to your state filings.

Weekends, Holidays, and Disaster Extensions

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

Additionally, when a geographical area is officially designated as a disaster area, tax due dates are typically extended for affected residents. You can verify whether your area has been designated as a disaster zone and check for updated filing extensions by visiting the following official websites:

Keep Your 2026 Taxes on Track

Proactive planning is the best way to avoid surprise penalties and keep your financial goals on track. If you have questions about your safe harbor estimates or want to review your current withholding, the team at Christiansen Accounting is here to help. Contact our office today to schedule your fall tax planning consultation.

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