TL;DR: If you'll owe about $1,000 or more in federal tax and little or nothing is being withheld, the IRS expects four payments a year, not one in April. Missing them can add a penalty. The fourth 2026 payment is due January 15, 2027.
Most grad students first hear about estimated taxes in April, when they owe far more than expected. Nothing was withheld from a fellowship stipend, the tax bill arrives all at once, and there may be a penalty on top for not paying earlier.
The IRS runs on a pay-as-you-go system. If no employer is withholding tax for you, you're expected to send in payments during the year. That's what "quarterly estimated taxes" means. This guide explains who needs to do it, when, how to work out how much, and how to avoid penalties even if you're starting late. It's general information, not tax advice, and applies to U.S. tax residents. International students on F-1 or J-1 visas often have tax withheld on fellowship income already, so see our international student tax guide.
Do you need to pay estimated taxes?
Generally, you should make estimated payments if you expect to owe $1,000 or more in federal tax for the year after subtracting withholding and credits.
For grad students, that typically describes you if:
- You're on a fellowship or stipend with no withholding, as most U.S. citizens and residents are
- You have taxable fellowship income plus some wages, and the withholding on the wages doesn't cover everything
- You have side income from tutoring, freelancing, or consulting
You probably don't need to if all your income is assistantship wages and your paychecks already have enough tax withheld, or if your taxable income is small enough that you'd owe less than $1,000.
For how fellowship income is taxed in the first place, see Yes, Your Stipend Is (Probably) Taxable.
The four payment deadlines
Despite the name, the four deadlines aren't evenly spaced quarters. For the 2026 tax year, they are:
| Payment | Income period covered | Due date |
|---|---|---|
| 1 | Jan 1 – Mar 31 | April 15, 2026 |
| 2 | Apr 1 – May 31 | June 15, 2026 |
| 3 | Jun 1 – Aug 31 | September 15, 2026 |
| 4 | Sep 1 – Dec 31 | January 15, 2027 |
(Official: IRS. If a date falls on a weekend or holiday, it moves to the next business day.)
If you're reading this in late September 2026, the third payment date has just passed. You can still make a payment now. Paying late costs less in penalties than never paying, and the final payment is due January 15, 2027. If you file your full return and pay everything you owe by January 31, 2027, you can skip the fourth payment.
How much do you have to pay?
You don't have to pay exactly what you'll owe. The IRS gives you safe harbor rules: if you pay at least one of the following through withholding and estimated payments combined, you generally avoid the underpayment penalty.
- 90% of this year's tax, or
- 100% of last year's tax (110% if your last-year adjusted gross income was over $150,000)
The second option is especially useful because it's predictable. If you know last year's tax, you can divide it by four and pay that each quarter, even if this year's income turns out higher. You may still owe the balance at filing time, but no penalty.
If you owed no tax last year, you generally won't owe an underpayment penalty this year, as long as you were a U.S. citizen or resident for all of last year and it was a full 12-month tax year. That's a lifeline for many first-year students whose income the previous year was low or nonexistent.
A simple way to estimate
Form 1040-ES has a worksheet, but the logic is straightforward:
- Estimate your taxable income for the year: taxable stipend and wages, minus the standard deduction ($16,100 for a single filer in 2026, Official: IRS).
- Figure the federal income tax on that amount.
- Subtract any tax that will be withheld from paychecks.
- Divide what's left by the number of payments remaining.
You can skip the arithmetic with our quarterly estimated tax estimator, which applies these rules and the 2026 dates to your own numbers.
Here's an illustration (Estimated, ignoring credits, state tax, and other income):
- Taxable stipend for the year: $30,000
- Minus standard deduction: $16,100 → taxable income $13,900
- Federal income tax: about $1,420
- Divided across four payments: about $355 per payment
In this example, the federal tax works out to under 5% of the gross stipend, but that percentage shifts with your income, credits, and other sources, so don't reuse it blindly. Run the worksheet or use your tax software's estimator for your own numbers.
How to pay
You have several free or low-cost ways to send a payment to the IRS:
- IRS Direct Pay takes money directly from your bank account with no fee.
- Your IRS online account lets you view payments and make new ones.
- EFTPS, the federal tax payment system, requires enrollment ahead of time.
- Mail a check with a Form 1040-ES payment voucher.
Whichever method you use, select 1040-ES / estimated tax as the payment type and choose the correct tax year. Keep the confirmation. You'll need the amounts when you file.
If your income isn't steady
Grad student pay is often lumpy. You might have a fellowship in the fall, a TA job in spring, and a summer stipend, or you might start your program mid-year. If most of your income arrives late in the year, paying equal amounts each quarter can overshoot early on.
The IRS provides the annualized income installment method (on Form 2210, Schedule AI) for this. It lets you base each payment on income actually earned to date, which can reduce or eliminate penalties when income is uneven. Tax software can usually calculate this if you tell it when you received your income.
A withholding shortcut
If you have a W-2 job, whether a TA appointment or a summer job, you can raise your withholding on Form W-4 to cover your fellowship income too. Withholding is generally treated as if it were paid evenly through the year, no matter when it actually happened. So bumping up withholding late in the year can fix an earlier shortfall in a way that a late estimated payment can't.
This is often the easiest approach for students who'd rather not track quarterly deadlines.
What happens if you don't pay
The IRS charges an underpayment penalty calculated on how much you were short and for how long, using an interest rate it sets each quarter. It's not typically huge for grad-student income levels, but it's avoidable, and it applies on top of the tax you owe. You figure it on Form 2210, and tax software usually does this for you.
The penalty doesn't apply if you owe less than $1,000, or if you meet a safe harbor above. If you have a good reason for paying late, such as a disaster or serious illness, you can ask the IRS to waive it.
Don't forget your state
Many states have their own estimated-tax rules with similar thresholds and deadlines. Some withhold from fellowship payments; many don't. Check your state revenue department's website, and see our state taxes guide for how moves and part-year residency affect this.
A simple plan for first-year students
- Find out if your fellowship payments have withholding. Look at a pay stub or ask payroll.
- Check whether the prior-year safe harbor applies. If you owed no tax last year, you may be penalty-free this year.
- Estimate the year's tax with the worksheet or your software.
- Move money into a separate savings account each pay period so you're never scrambling.
- Pay by the deadlines, or raise your W-4 withholding if you have wage income.
- Keep records of every payment, including dates and amounts.
Our article on building an emergency fund on a stipend covers how to make room for a tax reserve on a tight budget.
Common mistakes
- Waiting until April. By then, the penalty is already running.
- Picking the wrong tax year. The January payment is for the prior tax year's fourth installment, so choose the year it belongs to when you pay online, or it can be credited to the wrong return.
- Assuming no W-2 means no tax due. See our stipend taxability guide.
- Skipping the safe harbor check. It can save you from penalties even when your total tax ends up higher than expected.
- Forgetting state estimated payments.
Where to look next
The IRS explains the rules in Publication 505, Tax Withholding and Estimated Tax, and provides Form 1040-ES with a worksheet. For the full filing picture, see our guide to filing your taxes as a grad student.
This article is for general information and is not tax, legal, or financial advice. Tax rules, dates, and penalty rates change, and individual situations vary, so confirm details with the IRS or a qualified tax professional.