About

About EstQuarterly

A free, no-sign-up calculator that answers one practical question: how much should I send the IRS each quarter to avoid the estimated-tax underpayment penalty?

If you have income that isn't fully covered by withholding — freelance and 1099 work, a side business, investment or rental income, large capital gains — you may owe estimated taxes four times a year. Pay too little and the IRS adds an underpayment penalty (interest on what you should have paid). EstQuarterly computes your safe harbor and the per-quarter payment that keeps you penalty-free.

How it works

The federal safe harbor (IRC §6654, IRS Form 2210 and Publication 505) waives the penalty when your withholding plus timely estimates cover the smaller of 90% of this year's tax or 100% of last year's tax — 110% if your prior-year AGI exceeded $150,000 ($75,000 if married filing separately). There's also a de-minimis rule: if you'll owe under $1,000 after withholding, no penalty applies. All math runs in your browser; nothing is sent anywhere.

What it is not

This is a planning estimate, not tax advice. It assumes the standard four equal installments and a full 12-month prior tax year, and it does not compute the exact dollar penalty (which uses the IRS rate that resets each quarter) or handle the annualized-income method for uneven income. Always confirm against Form 2210/Pub 505 or a tax professional before you pay.