# Q3 Estimated Tax Deadline: How to Use Safe Harbor Rule Avoid underpayment penalties by calculating September 15 payment correctly. - **Source:** [Money Crashers](https://brifing.si/source/e5785ea7-b258-42a4-bb41-1513de5acde0) - **Published:** 2026-09-14 - **Topic:** [Finance](https://brifing.si/c/finance) - **Original article:** - **On Brifing:** https://brifing.si/s/8c0317fc-f303-4e34-9a7e-284c8b9ff7c6 ## Understanding the September 15 Deadline The third quarterly estimated tax payment for 2023 is due September 15 for taxpayers who expect to owe $1,000+ after withholding. This primarily affects self-employed individuals, landlords, retirees with IRA distributions, and investors with capital gains. The IRS requires these payments to ensure tax liabilities are paid throughout the year rather than just at filing time. Missing deadlines triggers penalties calculated daily like interest charges. ## The Safe Harbor Calculation Method To guarantee penalty avoidance, pay either: 1) 100% of last year's total tax (110% if AGI exceeded $150,000), divided into four equal installments, or 2) 90% of current year's estimated tax. The first method is foolproof since it uses known numbers from your previous Form 1040. For most taxpayers, dividing last year's total tax by four provides a reliable payment amount regardless of current income fluctuations. ## Special Rules for Higher Earners Taxpayers with previous year adjusted gross income over $150,000 ($75,000 if married filing separately) must pay 110% of last year's tax liability to qualify for safe harbor protection. This higher threshold accounts for potentially larger tax obligations. The rule applies even if current year income decreases significantly. Your 2022 Form 1040 line 24 shows the exact amount to use for calculations. ## Who Needs to Make Estimated Payments? Quarterly payments apply to anyone expecting to owe $1,000+ after withholding and refundable credits. This includes gig workers, sole proprietors, partners, S-corp shareholders, and investors with significant capital gains. Even W-2 employees may need to pay if they have side income or insufficient withholding. The IRS evaluates based on tax situation, not employment type. ## How to Submit Payments Easily The fastest method is IRS Direct Pay (no login required), selecting 'Estimated Tax' and 2023 as the tax year. Payments pull directly from bank accounts within 1-2 business days. Existing EFTPS users can schedule payments there. Both methods provide immediate confirmation. Mailing paper checks with Form 1040-ES is also accepted but takes longer to process. ## Catching Up on Missed Payments If you missed April or June payments, submit them immediately with your September payment to minimize penalties. The IRS calculates underpayment penalties daily for each late installment. Increasing W-2 withholding can also offset missed payments since the IRS treats withholding as evenly distributed throughout the year, regardless of when it's actually withheld. ## Documentation and Record-Keeping Maintain records of all estimated payments including dates, amounts, and confirmation numbers. These will be crucial when filing your 2023 return to claim credit for payments made. The IRS Form 2210 helps calculate any underpayment penalties if you didn't meet safe harbor requirements. Payment history is available in your IRS online account. ## Planning for January and Beyond Mark your calendar for the final 2023 estimated payment due January 15, 2024. Using the safe harbor method means you'll pay the same amount as September. This approach transforms tax planning from guesswork into a predictable system, preventing April surprises. Remember that safe harbor only covers underpayment penalties - you'll still reconcile actual tax due when filing. ## Sources covering this story - https://www.moneycrashers.com/q3-estimated-tax-safe-harbor/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._