Quarterly Estimated Taxes: How They Work for Business Owners

When you were an employee, tax ran on autopilot: your employer withheld it from every paycheck and April was a settling-up. As a business owner nobody withholds anything, but the IRS still expects to be paid as you earn, in four installments. Miss them and next spring's return carries a penalty that is really interest, computed installment by installment, whether or not you knew the rule existed.

The system is more forgiving than it looks. There are safe harbors that let you pay a known amount and stop worrying about the projection, a method for seasonal businesses, and, for S-corp owners, a year-end fix most people have never heard of.

Who has to pay, and the 2026 due dates

You must make estimated payments if you expect to owe at least $1,000 for the year after subtracting withholding and refundable credits, and your withholding will cover less than the safe-harbor amounts below. That covers sole proprietors, single-member LLC owners, partners and S-corp shareholders, because pass-through profit reaches your personal return with no tax taken out. The S-corp itself pays no federal income tax, so the estimates are yours, not the company's.

The four "quarters" are not equal. The IRS estimated tax schedule for 2026 is:

Owners who set a reminder "every three months" are late for the June payment every year. If a due date falls on a weekend or holiday, the next business day counts. You can pay more often than quarterly if it helps cash flow, as long as the cumulative total is in by each due date.

The safe harbors: 90%, 100% or 110%

You avoid the penalty entirely if, by each due date, your payments and withholding add up to the smaller of two targets: 90% of the tax you will actually owe for 2026, or 100% of the total tax shown on your 2025 return. If your 2025 adjusted gross income was more than $150,000 ($75,000 married filing separately), the prior-year target is 110% instead of 100%. And if you owe less than $1,000 after withholding when you file, there is no penalty regardless.

The prior-year safe harbor is the one we lean on for most owners, because it turns a forecast into a known number. Take last year's total tax from the 1040, multiply by 100% or 110%, subtract expected withholding, divide by four, and you are done arguing with the projection. The cost is that if 2026 is a much better year, you will owe a large balance in April 2027: no penalty, but a real cash requirement. The current-year method is better when profit is falling, because paying 100% of a big prior year means lending the IRS money interest-free.

The safe harbor is measured installment by installment. Paying nothing until January and then sending the whole prior-year amount does not work; the first three installments were still late.

How to compute the payment from your P&L

Under the current-year method the source document is your profit and loss statement, which is one reason clean monthly books matter. The steps:

1. Take year-to-date net profit from the P&L and project it to a full year. Through August, year-to-date times 1.5 is a reasonable start, adjusted for anything you know is coming.
2. Add the adjustments the books do not show: owner's health insurance, retirement contributions, depreciation on assets bought this year, and personal items that landed in the business accounts.
3. Compute self-employment tax if you are a sole proprietor or partner: 92.35% of net profit times 15.3%, with the 12.4% Social Security portion stopping at $184,500 of earnings for 2026. Half of that tax is a deduction.
4. Add other household income (a spouse's W-2, interest, capital gains), subtract the standard deduction ($32,200 joint, $16,100 single for 2026) or itemized deductions, subtract the 20% qualified business income deduction, and apply the 2026 brackets.
5. Add income tax and self-employment tax, subtract withholding and credits, and take 90% of the result (or the prior-year figure if lower). Divide by four, then true it up each quarter as the P&L changes.

Our guide to reading a profit and loss statement covers the first step; the rest is arithmetic we run every quarter.

Worked example: a landscaping business in Brandon

Maria owns a landscaping company organized as a single-member LLC, so her profit lands on Schedule C. Through August 31, 2026 her P&L shows $96,000 of net profit, and she expects about $145,000 for the year. Her husband earns $60,000 in wages with $5,200 of federal withholding. They file jointly with the standard deduction. Their 2025 return showed $26,400 of total tax on adjusted gross income of $132,000.

Maria can legally pay $5,300 a quarter and owe no penalty, but she will then write a check for roughly $13,300 in April 2027. If she is disciplined about setting money aside, that is a reasonable choice; if she would rather not face a five-figure bill, she pays the $7,643. Either way, her 2026 AGI will be about $195,000, so for 2027 her prior-year safe harbor rises to 110% of the 2026 tax: about $43,700 before withholding.

Seasonal businesses and the annualized method

A pool company or a tax preparer earns most of its profit in a few months, and four equal installments mean overpaying early in the year. The annualized income installment method, on Schedule AI of Form 2210, lets you compute each installment from the income actually earned through the end of that period. Income through March 31 is multiplied by 4, through May 31 by 2.4, through August 31 by 1.5, and the full year by 1; the required cumulative payments are 22.5%, 45%, 67.5% and 90% of the tax on each annualized figure.

The method is precise but demanding: you need accurate books closed at each of the four cutoffs, and once you use it for one installment you must use it for all of them. For a business that earns most of its profit between May and September it can eliminate a penalty that equal installments would create. For steady income it adds work for no benefit.

What the penalty costs, and how to pay

The penalty is figured on Form 2210 as interest on each installment's shortfall, from its due date until it is paid or April 15, at the IRS underpayment rate: 7% per year for the quarter beginning October 1, 2026 (6% for part of the year). Underpaying a single $7,000 installment by three months costs roughly $120; underpaying every installment by $7,000, so $28,000 short by January, costs about $1,300. That is not catastrophic, but it buys nothing, and it stacks with the failure-to-pay penalty if the April balance goes unpaid too. There is no "I didn't know" exception; waivers are limited to casualty, disaster or other unusual circumstances, or retirement after age 62 or disability with reasonable cause.

Paying is the easy part. IRS Direct Pay is free, needs no account, and lets you choose "estimated tax" and the 2026 tax year. EFTPS requires enrollment but keeps a full payment history and suits businesses already depositing payroll taxes through it. Your IRS Online Account shows every payment posted. Save the confirmation number; a payment applied to the wrong year is the most common reason for a notice, and the confirmation is what fixes it.

The S-corp owner's late-year fix

If you own an S-corp, you have a tool a sole proprietor does not. Federal income tax withheld from wages is treated as paid evenly across the four due dates, no matter when in the year it was actually withheld. An owner who realizes in November that K-1 income will be far higher than planned can have the company withhold an extra $10,000 or $15,000 of federal income tax from December payroll, and the IRS treats a quarter of it as paid in April, June and September. The underpayment for those installments disappears retroactively.

A late estimated payment cannot do that; it only stops interest from the day it is made. This is one of the quieter advantages of running real owner payroll, and it works just as well for a spouse's W-2 job: raise the withholding on a new W-4 for the last few paychecks of the year. Our article on LLC vs. S-corp taxes covers the other trade-offs.

What usually goes wrong

The same handful of mistakes account for nearly every penalty we see. Owners treat the June installment as due in July. They compute the payment once in April and never revisit it as the business grows, then discover the 110% rule applies because last year's AGI crossed $150,000. They pay the right total on the wrong schedule, often nothing until September and then a catch-up. They apply a Direct Pay payment to the wrong tax year. And in the first S-corp year, they keep paying estimates on the whole profit while also having tax withheld from the new salary, overpaying by thousands.

Underneath most of these is a bookkeeping problem: if the P&L is three months behind, no one can project the year. Estimated taxes are the most immediate reason to keep the books current, which is why we run the projection as part of the monthly close rather than separately.

When to get help

If your profit changes materially from year to year, if a spouse has W-2 income, or if you elected S-corp status and are juggling salary withholding and K-1 income, a quarterly projection built from actual books is worth far more than it costs. We prepare it each quarter, tell you the amount and the date, and adjust S-corp withholding when that is the cleaner fix, as part of our business tax planning and preparation service.

If you have already missed installments this year, pay now to stop the interest, then decide whether the safe harbor or the annualized method reduces what is owed. Request a 20-minute fit call with your year-to-date P&L and last year's return, and we will tell you what the September and January payments should be.

Jenny Gao, CPA, EA

Founder of Balance Partners. Florida-licensed CPA and IRS Enrolled Agent with more than a decade of accounting and tax experience. Jenny writes and reviews every guide on this site. About Jenny

This article is general educational information for U.S. business owners and is not accounting, tax, legal, payroll or financial advice for your situation. Rules change and vary by entity, state and facts. Balance Partners, LLC does not provide audit, review or other attest services. Last reviewed September 14, 2026.