What Is the Safe Harbor Rule for Taxes? Tests Explained

Key Terms for First-Time Filers

Term	What it means
Safe harbor	Conditions that protect you from a penalty
Adjusted gross income (AGI)	Income minus certain adjustments, shown on your tax return
Withholding	Tax your employer takes from each paycheck
Estimated tax	IRS payments on income with no withholding, such as self-employment, interest, dividends or rents

You pay estimated tax with Form 1040-ES. IRS Publication 505 covers withholding and estimated tax in depth.

Safe Harbor Rule Tests to Avoid the Penalty

Meeting any one of these IRS underpayment penalty tests avoids the penalty.

Note: First-time filers and short prior-year filers may only use the Small Balance Due and the 90% Tests

Test	What you need	Who it applies to
Small balance due	Total tax, minus withholding and refundable credits, is under $1,000.	Everyone
90% of current-year tax	Paid at least 90% of this year’s tax	Everyone
100% of prior-year tax	Paid at least 100% of last year’s tax	Prior-year AGI of $150,000 or less ($75,000 if married filing separately)
110% of prior-year tax	Paid at least 110% of last year’s tax	Prior-year AGI over $150,000 (over $75,000 if married filing separately)

For the percentage tests, you only need the smaller amount.

Example With AGI Over $150,000

Say your prior-year total tax was $20,000 and your AGI was $180,000. If you haven’t paid 90% of your current year’s tax, you are protected by the safe harbor rule if you have paid at least $22,000 (110% of $20,000) this year, or $5,500 per quarter if paid evenly.

How Withholding and Estimated Payments Count

Publication 505 says the IRS counts withholding plus on-time estimated payments. The IRS penalty page notes you can raise job withholding with a new Form W-4. The IRS generally treats withholding as paid evenly across the year, even if it happens late. That makes a Q4 W-4 increase a useful fix for earlier shortfalls. If you earn cash income or other income with no withholding, you’ll likely need estimated payments.

Estimated Tax Due Dates

IRS Publication 505 splits the year into four payment periods, each with its own due date. The IRS estimated taxes guide says you can be penalized for underpaying in any period, even if you’re due a refund. If a due date falls on a weekend or legal holiday, paying the next business day is on time.

Payment	Covers income earned	Usually due
First	January 1 – March 31	April 15
Second	April 1 – May 31	June 15
Third	June 1 – August 31	September 15
Fourth	September 1 – December 31	January 15 of the following year

Under the January payment rule in Publication 505, you can skip that payment if you file and pay in full by the end of January. Learn more about how to pay estimated taxes online.

If You Miss a Safe Harbor

Form 2210 helps you figure whether you owe the penalty and how much. Most people don’t need to file it, because the IRS can calculate the penalty and bill you. You file it to request a waiver or to use the annualized income method.

Special Safe Harbor Rule for Farmers and Fishers

Farmers and fishers get a lower target if at least two-thirds of their gross income comes from farming or fishing. With no 110% rule, the Form 1040-ES farmer rules use the smaller of 66 2/3% of this year’s tax or 100% of last year’s. They file Form 2210-F and, per the IRS penalty page, can skip estimated payments by filing and paying all tax by March 1.