What is Estimated Taxes?
Estimated taxes are quarterly payments you make directly to the IRS on income that has no withholding — freelance profit, business income, investment gains.
How it works
You project your year's tax, divide it into four, and pay via Form 1040-ES by mid-April, mid-June, mid-September, and mid-January. It's the self-employed version of a paycheck's withholding, and skipping it invites an underpayment penalty.
A quick example
What people get wrong
The easiest safe harbor: pay 100% of last year's tax (110% if you're a higher earner) across your four payments. Hit that and you avoid penalties no matter how much you actually end up owing.