Self‑employed people, and side‑hustlers often learn the hard way that nobody is withholding taxes from their income. If you don’t set money aside and pay quarterly estimated taxes , the IRS (and CRA in Canada) can hit you with a painful bill plus penalties at the end of the year. A self‑employed quarterly tax calculator helps you avoid that by turning your expected income and deductions into four predictable payments you can actually plan for.​ This guide explains how quarte