Quarterly Estimated Taxes: Safe Harbors & Deadlines

Nobody withholds tax from a freelance invoice, so the IRS asks you to do it yourself four times a year. The rule that protects you from penalties is generous — and the calendar it runs on is not the one you'd guess.

Last verified 2026-07-21

The rule that lets you stop guessing

US income tax is pay-as-you-go. An employee satisfies that through withholding; a freelancer has to send payments in during the year, and underpaying triggers an interest-style penalty even if you settle in full at filing.

Safe harbor removes the guesswork. Pay the lesser of 90% of this year's total tax or 100% of last year's — 110% if your prior-year AGI was over $150,000 — and no penalty applies, no matter how much you end up owing.

The prior-year branch is the one to build on, because you already know that number on January 1. The current-year branch requires forecasting a year you haven't lived through. If you have a spectacular year, safe harbor means you can pay based on last year's smaller tax, keep the difference earning interest, and settle the balance at filing without penalty.

They're called quarters and only one of them is

The four payments are due April 15, June 15, September 15, and January 15 of the following year. The periods they cover are three months, two months, three months, and four months.

So income earned in April is due in June, six weeks later — while income earned in September isn't due until the following January. Assuming even three-month blocks means underpaying the second period, and the penalty is calculated period by period, so a correct annual total doesn't repair it.

There's a useful escape hatch if your income is lumpy: tax withheld from a W-2 is treated as paid evenly across the year, whenever it was actually withheld. Someone with a job alongside their freelancing can increase withholding late in the year and have it credited as though it arrived in instalments, which can cure an earlier underpayment that an estimated payment couldn't.