What is the estimated-tax safe harbor and how does it protect a self-employed person?

The safe harbor is a set of payment levels that protect you from underpayment penalties even if you end up owing more at filing. You're generally safe if your quarterly estimated payments total at least 90% of this year's tax, or 100% of last year's total tax — whichever is smaller. If your prior-year adjusted gross income exceeded $150,000, the second figure rises to 110% of last year's tax. The beauty of the safe harbor is certainty: pay the right amount based on last year's known number and you avoid penalties no matter how much your income grows. So in a year your income jumps, paying 100% (or 110%) of last year's tax keeps you penalty-free while you settle the rest by the filing deadline. Map your quarterly numbers with wealthserene.com/tools/self-employed-hub.