If you're self-employed, a freelancer, or have significant income that isn't subject to withholding — investment income, rental income, or side business earnings — the IRS expects you to pay tax on it four times a year, not just once at filing time. Here are all four 2026 due dates. * The first quarterly payment, covering income earned January through March, is due April 15, 2026 — the same day as the regular tax filing deadline. The second payment, covering April and May, is due June 15, 2026, despite covering only two months instead of three (the IRS's quarters for estimated tax purposes don't split evenly). The third payment, covering June through August, is due September 15, 2026. * The fourth and final payment covers September through December, but it isn't due until January 15, 2027 — the following calendar year. If any of these dates falls on a weekend or federal holiday, the deadline automatically shifts to the next business day. * Skipping or underpaying these quarterly amounts can trigger an underpayment penalty even if you pay everything owed in full by the April filing deadline — the IRS calculates the penalty based on when the money should have arrived, not just the year-end total. Generally, you avoid the penalty if you've paid at least 90% of this year's tax bill or 100% of last year's (110% if your prior-year income was high) through withholding and estimated payments combined.