If you're self-employed, a business owner, or receive non-W-2 income, the Q3 estimated tax deadline on September 15, 2026, is fast approaching. Here is what you need to know to avoid IRS underpayment penalties and keep your finances on track.

f you're self-employed, a business owner, or receive non-W-2 income, the Q3 estimated tax deadline on September 15, 2026, is fast approaching. Here is what you need to know to avoid IRS underpayment penalties and keep your finances on track.