Quick answers
Is the calculator really free? Yes: free, no sign-up, and it runs entirely in your browser. Nothing you type is sent to any server.
Why does my accountant's number differ? The calculator models federal SE and income tax with the standard deduction and QBI, plus an optional flat state rate. Credits, itemizing, W-2 interplay, and state brackets can move the real answer; see how Sero computes.
When does the app launch? Tax season 2027 on iPhone. The app tracks payouts across platforms, keeps the safe-to-spend number live, and reminds you before quarterly deadlines.