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September 2025 Individual Due Dates

Written by Kohari Gonzalez Oneyear & Brown | Aug 26, 2025 12:30:00 PM

 

The tax deadlines for September 2025 include tip reporting and estimated tax payments.  Learn the safe harbor regulations, how to avoid penalties, and how to plan for 2026.

2025 Fall and 2026 Tax Planning

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September 10 - Report Tips to Employer

If you are an employee who works for tips and received more than $20 in tips in August, you must report them to your employer using IRS Form 4070 by September 10.  Your employer is required to deduct FICA and income tax withholding for these tips from your normal pay.  If your regular wages are insufficient to pay FICA and tax withholding, your employer will record the uncollected withholding in box 8 of your annual W-2.  When you file your annual return, you will be obligated to pay any uncollected withholdings.

September 15 - Estimated Tax Payment Due

The third installment of the 2025 individual anticipated taxes is due.  Our tax system is a "pay-as-you-earn" model.  To help taxpayers comply with the "pay-as-you-earn" rule, the government has provided numerous options.  This includes:

  • Payroll withholding for employees.
  • Pension withholding for retirees.
  • Estimated tax payments for self-employed and non-withholding income sources.

When a taxpayer fails to prepay a safe harbor (minimum) amount, they may face an underpayment penalty.  The penalty is equal to the federal short-term rate + 3 percentage points, and it is assessed quarterly.

 The federal tax code does offer options to avoid the underpayment penalty.  If the underpayment is less than $1,000 (the de minimis amount), there is no penalty imposed.  In addition, the law permits "safe harbor" prepayments.  There are two safe harbors.

  • The first safe harbor refers to the current year's tax payable.  If your payments equal or surpass 90% of what is outstanding in the current year, you can avoid the penalty.
  •  The second safe harbor is based on the previous tax year.  This safe harbor typically covers 100% of the prior year's tax liability.  However, for taxpayers with AGIs more than $150,000 ($75,000 for married taxpayers filing separately), the previous year's safe harbor is 110%.

Assume you have a $10,000 tax liability and $5,600 in prepayments.  As a result, you owe an additional $4,400 on your tax return.  To determine whether you owe a penalty, check to see if you fall under the first safe harbor exception.  Because 90% of $10,000 equals $9,000, your prepayments fell short of the threshold.  You cannot avoid the penalty under this exception.

However, in the preceding situation, the safe harbor may still apply.  Assume that your previous year's tax was $5,000.  Because you prepaid $5,600, which is more than 110% of the previous year's tax (110% = $5,500), you are eligible for this safe harbor and can avoid the penalty.

This example emphasizes the significance of making enough prepayments, especially if you have a significant increase in income.  This is typical when there is a significant gain from the sale of stock or property, when large bonuses are paid, when a taxpayer retires, and so on.  The safe harbor exception to the penalty requires timely payment of each required estimated tax installment.  If you have any queries about your safe harbor calculations, please call this office as soon as possible.

Caution: State de minimis quantities and safe harbor estimate regulations may differ from federal estimates.  Please contact this office for specific state safe harbor rules.

Weekends & Holidays:

If a due date comes on a Saturday, Sunday, or legal holiday, it is automatically extended to the following working day that is not a legal holiday.

Disaster Area Extensions:

Please keep in mind that when a geographic area is classified as a disaster area, deadlines will be extended.  For further information on whether an area has been declared as a disaster area and the filing extension dates, please visit the following websites:

FEMA: https://www.fema.gov/disaster/declarations

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

September 2025 Business Due Dates

September 2025 company tax deadlines include S corporation and partnership files with extensions, corporate projected payments, and payroll tax deposits due on September 15.

September 15 - S Corporations

File a 2024 calendar year income tax return (Form 1120-S) and pay any taxes owed.  This deadline applies only if you requested an automatic 6-month extension.  Provide each shareholder with a copy of their Schedule K-1 (Form 1120-S) or a substitute Schedule K-1, as well as, if applicable, Schedule K-3 (Form 1120-S) or substitute Schedule K-3.

September 15 - Corporations

Deposit the third installment of the 2025 projected income tax for calendar-year corporations.

September 15 - Partnerships

Submit a 2024 calendar year return (Form 1065).  This deadline applies only if you were granted a 6-month extension.  Give each partner a copy of their Schedule K-1 (Form 1065) or a substitute Schedule K-1, as well as Schedule K-3 (Form 1065), if applicable.

September 15 - Social Security, Medicare and Withheld Income Tax

If you are an employer and the monthly deposit regulations apply, the deadline for submitting your Social Security, Medicare, and withheld income tax deposits for August 2025 is September 15.  This is also the deadline for the nonpayroll withholding deposit for August 2025, assuming the monthly deposit rule applies.

Weekends & Holidays:

If a due date comes on a Saturday, Sunday, or legal holiday, it is automatically extended to the following working day that is not a legal holiday.

Disaster Area Extensions:

Please keep in mind that when a geographic area is classified as a disaster area, deadlines will be extended.  For further information on whether an area has been declared as a disaster area and the filing extension dates, please visit the following websites:

FEMA: https://www.fema.gov/disaster/declarations

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