Quarterly estimated taxes for high earners: the safe harbor, explained

Why estimated taxes exist

The US tax system is pay-as-you-go. Employees pay through withholding. If you earn 1099 income, own a pass-through business, or have significant investment income, no one is withholding for you, so the IRS expects you to pay during the year through quarterly estimated payments on Form 1040-ES.

Pay too little, too late, and you can owe an underpayment penalty. It works like interest, charged on each quarter’s shortfall for as long as it stays unpaid. Unlike most tax costs, it is almost entirely avoidable with a little planning.

Who has to pay

For 2026, you generally must make estimated payments if you expect to owe at least $1,000 after subtracting withholding and refundable credits, and your withholding and credits will fall short of the safe harbor amounts described below.

There’s one clean exception: if you were a US citizen or resident for all of 2025 and had no tax liability for the full 12-month year, you don’t owe estimated tax for 2026. That helps someone starting a business after a year with no income, but it rarely applies to established owners.

Many owners have a mix: a W-2 salary from an S corp or a hospital, plus K-1 or 1099 income on the side. Withholding from wages counts toward the safe harbor, so the question is whether that withholding plus any estimates reaches the required amount. Often the easiest fix is to raise withholding on the salary rather than juggle quarterly vouchers.

The 2026 due dates

Payments for a calendar tax year are due in four installments. The periods are uneven, which surprises people: the second payment covers only two months of income, and the fourth covers four.

• April 15, 2026 — income from January through March
• June 15, 2026 — April and May
• September 15, 2026 — June through August
• January 15, 2027 — September through December
• You can skip the January 15, 2027 payment if you file your 2026 return by February 1, 2027 and pay the full balance with it

The safe harbor rules

You generally avoid the federal underpayment penalty if your withholding plus timely estimated payments equal at least the smaller of these two amounts, paid in four equal installments:

• 90% of the tax shown on your 2026 return, or
• 100% of the tax shown on your 2025 return, which must cover a full 12 months
• If your 2025 adjusted gross income was more than $150,000 ($75,000 if married filing separately for 2026), the prior-year figure becomes 110%
• Farmers and fishermen (at least two-thirds of gross income from farming or fishing) use 66⅔% instead of 90% and aren’t subject to the 110% rule

Why the prior-year method suits high earners

The 90%-of-current-year test requires an accurate forecast of this year’s tax. That’s hard when income is lumpy: a large contract, a bonus, a K-1 that arrives in September, the sale of stock or a business.

The prior-year test removes the guesswork, because last year’s tax is a known number. Take the total tax from your 2025 return, multiply by 110% if your AGI was over $150,000, divide by four, and pay that each quarter.

A worked example: a consultant’s 2025 return showed total tax of $60,000 on AGI of $400,000. The safe harbor for 2026 is $66,000 (110% of $60,000), or $16,500 per quarter. If a strong year pushes her 2026 tax to $95,000, she owes no underpayment penalty — but she does owe the $29,000 difference when she files.

That last part matters. The safe harbor protects you from the penalty, not from the tax. If your income is rising, set aside cash for April so a large balance due isn’t a surprise.

How the penalty is actually figured

The penalty is computed separately for each installment, from its due date until the shortfall is paid or the return’s due date, whichever comes first. That’s why paying late is still better than not paying at all: the clock stops on the amount you catch up.

The rate is the IRS underpayment interest rate, which resets every quarter. For individuals it is 7% a year, compounded daily, for the fourth quarter of 2026. On a $10,000 shortfall from the September 15 installment that sits unpaid for four months, that’s roughly $230.

The IRS usually calculates the penalty and sends a bill. You use Form 2210 when you want to reduce it, for example by using the annualized method, or to request a waiver. Waivers are available when an underpayment resulted from a casualty, disaster or other unusual circumstance, or when you retired after reaching age 62 or became disabled in the current or prior year and the underpayment was due to reasonable cause.

Catching up in the fourth quarter

If it’s fall and you’ve underpaid, you still have options. Which one works best depends on where the income came from and whether you have wages.

• Increase W-2 withholding. Withholding is treated as paid evenly through the year unless you elect otherwise, so extra withholding from December wages can cover a shortfall from April. S corp owners can do this through a year-end payroll run.
• Use the annualized income installment method. If most of your income arrived late in the year, Schedule AI of Form 2210 matches the required payments to when income was actually earned. It takes more work but can reduce or eliminate the penalty for early quarters.
• Make the missed payment now. It won’t erase the penalty already accrued, but it stops more from building.
• Don’t skip January 15. Treat the fourth installment as mandatory unless you’re certain you’ll file and pay in full by February 1.

Common mistakes

• Using the 100% figure when your prior-year AGI was over $150,000 — the requirement is 110%
• Paying the safe harbor amount unevenly, such as one large payment in December; each installment is tested on its own
• Overlooking a prior-year overpayment applied to this year; it generally counts as paid on April 15, so it front-loads your first installment
• Assuming a big January payment fixes everything; the penalty is figured per installment, so an earlier quarter can still be short even if you’re due a refund
• Basing the calculation on income tax only; the “total tax” includes self-employment tax, the additional Medicare tax and the net investment income tax
• Assuming your state follows the federal rules; most states with an income tax have their own estimated payment schedules and safe harbors

Setting a schedule that holds up

For most business owners, the simplest reliable approach is to calculate the prior-year safe harbor after filing, schedule four equal payments through IRS Direct Pay or EFTPS, and then check actual income once in the summer and again in December to size the April balance.

When income is uneven or a large transaction is coming, a CPA or enrolled agent can compare the prior-year and annualized methods and adjust the plan mid-year. At Tally Tax, that review usually happens alongside year-end planning, so payments, retirement contributions and payroll are set together.

Frequently asked questions