This guide is for anyone whose income does not have enough tax withheld from it. Self-employed people and single-member LLC owners, households with a side business, rental income or investment gains, S corporation owners whose salary withholding does not cover their distributions, and anyone who paid a penalty last spring and would rather not repeat it. Every federal date and figure below was verified October 3, 2026 against the sources listed at the end. State rules are covered at the end of each section, because they differ from state to state.
The date
The fourth and final federal estimated payment for tax year 2026 is due Friday, January 15, 2027. That is a normal business day, so there is no weekend or holiday adjustment this year.
The federal schedule for 2026 was April 15, June 15 and September 15, 2026, and then January 15, 2027. The gaps are uneven on purpose, so if you set reminders by “every three months” you were late once already. Many states use the same four dates, but not all of them, so check your state’s schedule.
Who has to pay
Federal. You generally need to make estimated payments if you expect to owe $1,000 or more for 2026 after subtracting withholding and refundable credits. Withholding from a W-2 job or a pension counts toward that test, which is why a household with one salary and one side business sometimes needs no estimates at all and sometimes needs all four.
Your state. States with an income tax set their own test. Some use a dollar threshold like the federal one, and some use an income test. In practice, most people who need federal estimates also need state estimates, but the trigger is worded differently and it is worth checking both. States without an income tax have no individual estimates at all.
How safe harbor works
Safe harbor is the amount you can pay in during the year that protects you from an underpayment penalty, even if you end up owing more when you file. You still owe the balance on April 15. The safe harbor just means no penalty for the gap.
Federal. Pay the smaller of these two amounts through withholding and estimates, spread across the four due dates.
- 90 percent of your 2026 tax, or
- 100 percent of your 2025 tax. If your 2025 adjusted gross income was more than $150,000, or more than $75,000 if married filing separately, this becomes 110 percent of your 2025 tax.
The prior-year option only works if your 2025 return covered a full 12 months. The reason most planners lean on it is simple. Last year’s tax is a known number in January. This year’s tax is a projection until the books are closed.
Your state. State safe-harbor percentages and penalty rates often differ from the federal ones, and some states have no higher-income rule. We check your state’s rules alongside the federal ones in every projection.
An example without figures
A consultant (illustrative, not a client) had a strong 2026. Income roughly doubled, and nothing was withheld. The simplest safe harbor is to pay 100 percent of the 2025 federal tax across the four dates, with the last installment on January 15, 2027, and to follow the state’s prior-year rule on its own schedule. The consultant will owe a meaningful balance on April 15, 2027, because the safe harbor was based on a smaller year, but there is no underpayment penalty on it. The planning job is to make sure the cash for April is sitting in a tax account, not spent.
If 2025 was the bigger year instead, the current-year options are the ones to use, and that takes a projection.
The February 1 exception
You do not have to make the January 15, 2027 federal payment if you file your 2026 return and pay the entire balance due by February 1, 2027. For most people that is not realistic, because forms like the 1099 and the W-2 arrive right around that date. For a simple return with the figures already in hand, it is a legitimate way to combine the last estimate with the filing.
If you are behind
Three things to know. Estimated-tax penalties are figured installment by installment, so catching up in January does not erase a shortfall from June, but it does stop it from growing. Second, withholding is generally treated as if it had been paid evenly across the year, no matter when it was actually taken out. A W-2 earner with a side business can sometimes cure an earlier shortfall by raising withholding in the final paychecks of the year, which is a planning conversation, not a form. Third, a late payment is still worth making. The penalty is computed by days, so every day sooner is cheaper.
What to do before January 15
- Pull your 2025 federal and state returns and find the total tax on each. That gives you the 100 percent numbers, or the 110 percent federal number if your 2025 AGI was above the threshold.
- Add up what has already been paid in for 2026. Withholding from every W-2 and 1099-R, plus the three earlier estimates, federal and state separately.
- Estimate 2026 tax from the books, or from a projection if the books are not reliable. If the books are the problem, five signs your books need a cleanup is the place to start.
- Compare. The smaller of the safe-harbor amount and the projected amount, minus what is already paid in, is the January payment. Repeat for your state with its own rules.
- Pay federal electronically through IRS Direct Pay or your IRS online account, pay your state through its revenue department’s website, and keep the confirmations with your 2026 tax documents.
What EZ Financial Fitness does here
We do not send generic numbers. A tax projection takes your year-to-date income, withholding, earlier estimates and planned purchases and turns them into a federal and a state payment with the safe-harbor check shown. It is the first step in every Tax Strategy engagement.
What to do next
If you expect to owe and have not paid estimates this year, book a consultation before the end of December. January 15 arrives faster than the paperwork does, and the difference between a projection in December and a guess in January is usually the penalty.
Federal dates and figures in this article apply to tax year 2026 and were verified October 3, 2026 against the sources listed below. The IRS publishes the 2027 schedule in its 2027 Form 1040-ES and Publication 509, and this article is reviewed in the first two weeks of January. State rules differ, so verify your state’s before you act.