What are the quarterly estimated tax deadlines for 2026?

The 2026 federal estimated tax deadlines are: Q1 — April 15, 2026; Q2 — June 16, 2026; Q3 — September 15, 2026; Q4 — January 15, 2027. If a deadline falls on a weekend or holiday, it moves to the next business day.

What is the safe harbor rule for estimated taxes?

The safe harbor rule protects you from underpayment penalties if you pay either 100% of last year's tax liability (110% if your prior-year AGI exceeded $150,000) or 90% of the current year's actual tax liability. Most solopreneurs use the prior-year method because it requires no income forecasting.

What happens if I miss a quarterly estimated tax payment?

You'll owe an underpayment penalty calculated at the federal short-term interest rate plus 3 percentage points, applied to the underpaid amount for the days it was late. In 2026, this rate is approximately 7–8% annualized. The penalty is calculated per quarter, not as a single annual charge.

How do I pay quarterly estimated taxes?

The easiest method is IRS Direct Pay (pay.gov) — free, no account required, instant confirmation. You can also use EFTPS (Electronic Federal Tax Payment System) for recurring payments. Avoid mailing checks — processing delays can cause late payment issues.

Quarterly Estimated Taxes: Safe Harbor & System

# Quarterly Estimated Taxes: The Deadlines, the Safe Harbor Math, and the System That Prevents Surprises Quarterly estimated tax payments are due April 15, June 15, September 15, and January 15. Missing a deadline triggers an underpayment penalty. The safe harbor rule — paying 100% of last year's tax liability (110% if prior year AGI exceeded $150,000) — eliminates the penalty regardless of what you actually owe. The four quarterly deadlines are not equal — and missing one triggers a penalty calculated daily. The safe harbor rule, the annualized income method for variable income, and the 25-30% reserve system that prevents April surprises. Read the full article at https://solofilinglab.com/articles/quarterly-estimated-taxes-deadlines-safe-harbor-system