The third-quarter estimated tax payment deadline for both federal and Arizona taxes is September 15, 2026. Missing this deadline can result in underpayment penalties, so now is a good time to review your numbers.
Who Needs to Make Estimated Payments?
You generally need to make estimated tax payments if you expect to owe tax after subtracting withholding and credits. This commonly applies to:
- Self-employed individuals and independent contractors
- Business owners (S-Corps, partnerships, sole proprietors)
- People with significant income not subject to withholding (interest, dividends, rental income, capital gains)
- Those who under-withheld earlier in the year
Federal and Arizona Due Dates for 2026
- April 15, 2026
- June 15, 2026
- September 15, 2026 (upcoming deadline)
- January 15, 2027
How Much Should You Pay?
To avoid underpayment penalties, your total estimated payments plus withholding should generally equal at least:
- 90% of the tax you expect to owe for 2026, or
- 100% of the tax shown on your 2025 return (110% if your 2025 adjusted gross income was over $150,000)
Arizona has similar safe-harbor rules. Reviewing your year-to-date income and projecting the rest of the year will help you decide if an adjustment is needed.
What You Should Do Now
- Gather your year-to-date profit & loss or income records.
- Project your full-year income and deductions.
- Compare what you have already paid in estimates and withholding.
- Make an additional payment by September 15 if you are underpaid.
- Contact your tax advisor if you need help calculating the correct amount.
Need Help With Your September 15 Payment?
Vault Financials helps Arizona individuals and small business owners calculate and make accurate estimated tax payments so you stay compliant and avoid penalties.
Contact us today for assistance.
Disclaimer: This article is for educational purposes only. Tax rules can change and individual situations vary. Consult a qualified tax professional for advice specific to your situation.