# Estimated tax safe harbor rules: 90%, 100% and 110%

A plain guide to the estimated tax safe harbor: how much to pay each quarter so the IRS cannot charge you a penalty, with a worked example.

Published October 21, 2026.

If you work for yourself, nobody takes tax out of your pay. So the IRS asks you to send it money four times a year, called [quarterly estimated tax](https://rightobooks.com/blog/quarterly-estimated-taxes/). If you send too little, it can charge you a [penalty](https://rightobooks.com/blog/estimated-tax-penalty/).

The safe harbor is a simple rule that keeps you safe from that penalty. Pay a set amount on time, and you owe no penalty, even if your real tax turns out to be higher. For most people, the set amount is easy to find: **the total tax on last year's return**, split into four payments.

## The short version

For 2026, you are safe if your payments add up to the smaller of these two amounts ([Form 1040-ES](https://www.irs.gov/pub/irs-pdf/f1040es.pdf)):

1. 90% of your tax for this year (2026), or
2. 100% of your tax for last year (2025).

There is one change for higher earners. If your 2025 adjusted gross income (AGI) was over $150,000 ($75,000 if married filing separately), use 110% of last year's tax, not 100%.

Most people use the last-year number. You already know it, because it is on the return you filed. You do not have to guess how this year will go.

## Two words to know

**Tax** here means the total tax on your return, less refundable credits. It includes [self-employment tax](https://rightobooks.com/tools/self-employment-tax/), not only income tax. It is not your refund or the amount you owed when you filed ([IRS](https://www.irs.gov/payments/underpayment-of-estimated-tax-by-individuals-penalty)).

**AGI** (adjusted gross income) is a line on your Form 1040. It is your income after a few adjustments, before the standard deduction.

## An example

Priya is a consultant. (She is an example, not a real person.) On her 2025 return:

- Total tax: $38,000
- AGI: $120,000

Her AGI is under $150,000, so she uses 100% of last year's tax: $38,000. She divides it by four and pays **$9,500** on each due date.

Her business grows, and her 2026 tax comes to $52,000. Because she paid $38,000 on time, she owes no penalty. She still owes the other $14,000 when she files in April 2027. The safe harbor protects you from the penalty, not from the tax.

If Priya's 2025 AGI had been $190,000, she would use 110%: $38,000 × 110% = $41,800, or $10,450 a quarter.

## Pay on time, each quarter

The total is not the only thing that counts. The IRS checks each payment date on its own. For 2026 the dates are April 15, June 15 and September 15, 2026, and January 15, 2027. If you pay nothing until January, you can owe a penalty for the earlier quarters, even if the total is right ([Instructions for Form 2210](https://www.irs.gov/instructions/i2210)).

One exception helps people with a W-2 job too. Tax withheld from a paycheck counts as if it was paid evenly over the year. So if you or your spouse raise your withholding late in the year, it can cover earlier quarters.

If most of your income came late in the year, Form 2210 has a method (Schedule AI) that can lower the early payments.

## When you owe no penalty at all

You may not need the safe harbor at all:

- **You owe less than $1,000** after withholding when you file ([Instructions for Form 2210](https://www.irs.gov/instructions/i2210)).
- **You had no tax last year.** If your 2025 return showed no tax, you were a US citizen or resident all year, and it covered a full 12 months, you owe no penalty for 2026 ([Publication 505](https://www.irs.gov/publications/p505)). This often helps in your [first year of self-employment](https://rightobooks.com/blog/first-year-self-employed-checklist/).

## Special cases

- **Farmers and fishers** use 66 2/3% instead of 90%, and can make one payment by January 15, 2027 ([Publication 505](https://www.irs.gov/publications/p505)).
- **Married couples** whose filing status changed between years combine or split last year's tax. Publication 505 explains how.
- **Retirement, disability or a disaster** can be a reason for the IRS to waive the penalty ([IRS](https://www.irs.gov/payments/underpayment-of-estimated-tax-by-individuals-penalty)).

## Keep an eye on the April bill

The safe harbor makes the penalty go away. It does not make the tax go away. If your income goes up, [set aside money](https://rightobooks.com/blog/how-much-to-set-aside-for-taxes/) for the balance due in April.

[Righto](https://rightobooks.com/) helps with this. It keeps your profit up to date, reminds you of each federal estimated tax date and can add the dates to your calendar. You can also ask your own AI agent, such as Claude Code, how this year's profit compares with last year's. See [how agents work with Righto](https://rightobooks.com/agents/).

## What to do now

1. Find last year's return. Note the total tax and your AGI.
2. Multiply the tax by 100%, or 110% if your AGI was over $150,000.
3. Take away any tax you expect to have withheld this year.
4. Divide by four. That is your payment for each date.
5. If you are behind, pay the difference now. The penalty grows each day a payment is late.

For more help, see our [estimated tax dates tool](https://rightobooks.com/tools/estimated-tax-dates/). If your year has big changes, a tax professional can check your numbers.

[Righto](https://rightobooks.com/download/) is free, easy to use and needs no account.

## Sources

- [2026 Form 1040-ES, Estimated Tax for Individuals](https://www.irs.gov/pub/irs-pdf/f1040es.pdf), IRS
- [Publication 505 (2026), Tax Withholding and Estimated Tax](https://www.irs.gov/publications/p505), IRS
- [Instructions for Form 2210 (2025)](https://www.irs.gov/instructions/i2210), IRS
- [Underpayment of estimated tax by individuals penalty](https://www.irs.gov/payments/underpayment-of-estimated-tax-by-individuals-penalty), IRS