Free · US federal · tax year 2026
Quarterly Estimated Tax Guide
The rule, the four dates, and one worked example, every claim cited to an IRS form or the IRS Code.
What is in it
- Whether you owe estimated tax at all, and why that test is not the one that decides penalties
- The four due dates, and when the last one can be skipped
- The safe harbor, worked end to end with real numbers
- Four things you are allowed to do that most people never learn
- What the penalty actually is, and why no honest guide prints a rate for it
It explains the rule and works one example. It does not compute your number: that is what the Quarterly Tax Estimator is for. Everything in it is federal; your state, and sometimes your city, is a separate bill with separate rules.