How to Calculate and Pay Corporate Estimated Tax (Form 1120-ES)

Form 1120-ES is the IRS form corporations use to figure and pay quarterly estimated federal income tax. If your corporation expects to owe $500 or more for the year, you must project the liability, divide it into four installments, and send each payment electronically by the 15th day of the 4th, 6th, 9th, and 12th months of your tax year.¹

Which Corporations Have to Pay

The rule catches any corporation that expects total tax for the year, after credits, to reach $500.¹ C corporations are the main filers. S corporations get pulled in when they expect $500 or more from built-in gains tax, excess net passive income tax, or investment credit recapture.² Certain insurance companies and foreign corporations with U.S.-connected income are covered too. The IRS does not bill you for estimated tax. Projecting the number and paying on time is on the corporation.

Calculating the Quarterly Payment

The math lives on the Estimated Tax Worksheet in the Form 1120-ES instructions. You keep it in your records rather than filing it, but it drives every payment.

Start with projected taxable income for the year. Most corporations begin with last year’s return and adjust for expected changes in revenue, cost of goods sold, and operating expenses. Apply the flat 21% federal corporate rate. Subtract credits you expect to claim — research and development, foreign tax, general business credits are the common ones. What’s left is your estimated annual liability.

Divide that number by four. Each installment is one quarter of the total.

Revisit the projection every quarter. If revenue is running ahead or behind plan, refigure the remaining installments. Underpaying an early installment can still trigger a penalty even if the last two make up the difference, so a mid-year check is worth the time.¹ Hold on to the completed worksheet. You will reconcile it against actual liability when you file Form 1120.

Payment Due Dates

Installments are due on the 15th day of the 4th, 6th, 9th, and 12th months of the corporation’s tax year.¹ For a calendar-year corporation, that means:

1st installment: April 15
2nd installment: June 15
3rd installment: September 15
4th installment: December 15

When any of those dates falls on a Saturday, Sunday, or legal holiday, the deadline moves to the next business day. Fiscal-year corporations count from the start of their own tax year. A corporation with a July 1 year-start owes on October 15, December 15, March 15, and June 15.

Disaster Areas

The IRS regularly postpones estimated tax deadlines for corporations in federally declared disaster zones. Relief is automatic when the corporation’s principal place of business sits in the covered area.³ Corporations outside the zone whose records are stored inside it can call 866-562-5227 to request the same extension.

First-Year Corporations

A brand-new corporation has no prior return to lean on, which knocks out one of the two safe harbors. You have to estimate current-year tax as accurately as you can and pay on the schedule. If actual results outrun the projection, raise the remaining installments quickly. Underestimation in the first year is common, and the IRS will charge a penalty on the shortfall.

How to Submit Payments

Corporations must pay estimated tax by electronic funds transfer.¹ The Electronic Federal Tax Payment System (EFTPS) is the standard route. It’s free and run by the U.S. Department of the Treasury.⁴

Enrolling in EFTPS

Enroll before you owe. Go to eftps.gov, click Enrollment, and complete the steps. The IRS validates the information and mails a PIN to your address of record within five to seven business days.⁴ New corporations should enroll as soon as the Employer Identification Number arrives. Waiting until the first installment is due, then discovering you need a week for the PIN, is a mistake most people make exactly once.

Making a Payment

Log in with your EIN, PIN, and internet password. Choose federal tax deposit, enter form number 1120, the tax period, and the amount. Pick a settlement date. EFTPS needs at least one business day of lead time, so schedule ahead of the deadline rather than on it. When you authorize the transaction, the system returns an EFT acknowledgment number. Save it. That number is your proof of payment and what you’ll reference against bank statements or any IRS notice.

Same-Day Wire

If you miss the EFTPS scheduling window on the day a payment is due, you can pay through the Federal Tax Collection Service at your bank. Download the Same-Day Taxpayer Worksheet from eftps.gov, fill it out for each payment, and take it to your financial institution.⁵ Banks charge a fee, and cutoff times vary, so call first. After the wire clears, call 1-800-382-0045 for a 15-digit EFT number confirming receipt.⁶

When Income Is Uneven

Four equal installments work when income is steady. Corporations with seasonal or lumpy revenue can use either of two alternate methods that match payments to when income is actually earned.

The annualized income installment method recalculates each quarter’s required payment from the actual taxable income earned through the months preceding that quarter’s due date. It annualizes what you’ve booked so far and sizes the installment accordingly. Corporations whose income concentrates late in the year gain the most, because the method shifts payment obligations toward those later quarters.⁷

The adjusted seasonal installment method bases installments on the historical distribution of income across quarters. Ski resorts, landscapers, and tax preparers are the kind of businesses it fits. The math is more involved and you must demonstrate a genuine seasonal pattern. Both methods require Schedule A of Form 2220, attached to the annual return whenever the estimated tax on Part I, line 3 of Form 2220 is $500 or more, even if no penalty is owed.⁷ You can switch methods during the year if the pattern of income changes.

Safe Harbor Against Penalties

You avoid the underpayment penalty by paying, in timely installments, at least the lesser of:

100% of the tax shown on the current year’s return, or
100% of the tax shown on the prior year’s return, provided that return covered a full 12 months and showed some tax.⁸

The prior-year option is useful for a growing business. If last year’s tax was $50,000 and this year’s will come in around $120,000, paying $12,500 each quarter keeps you penalty-free even though a large balance is coming at filing.

Large Corporations

The IRS defines a large corporation as one with taxable income of $1 million or more in any of the three preceding tax years. In a controlled group, the $1 million threshold is split among members.⁸ Large corporations can use the prior-year safe harbor only for the first installment. The remaining three must be based on the current year’s tax.⁹ If the first installment based on the prior year turns out to be less than 25% of current-year tax, the shortfall gets made up in the second installment. Check the box on line 8 of Form 2220 and attach it to the return whenever you use the prior-year method for the first installment as a large corporation.

Underpayment Penalty

The penalty is effectively interest on the shortfall for the time it was outstanding. The IRS multiplies the underpayment by the applicable rate, prorated by the number of days late.¹⁰ For the first quarter of 2026 the rate is 7% for most corporations and 9% for large corporations.¹¹ The rate resets each calendar quarter based on the federal short-term rate.

In most cases the IRS calculates the penalty and sends a bill. You have to file Form 2220 yourself if you used the annualized income method, the adjusted seasonal method, or based the first installment on prior-year tax as a large corporation.¹² If a penalty notice looks wrong, call the number on the notice to ask for a review.

When You’ve Overpaid

If quarterly payments come in above actual liability, the overpayment surfaces on Form 1120. You have two options. Apply all or part of it toward next year’s estimated tax on line 37a, or request a refund on line 37b with direct deposit information for a faster payout.¹³ Once you elect to credit an overpayment forward, that choice is locked in.

If you know you’ve overpaid before filing, Form 4466 (Corporation Application for Quick Refund of Overpayment of Estimated Tax) gets the money back faster. The overpayment has to be at least 10% of expected liability and at least $500, and you file Form 4466 after the tax year ends but before you file the annual return.¹³

1
Internal Revenue Service. 2025 Instructions for Form 1120
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Internal Revenue Service. 2025 Instructions for Form 1120-S
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Internal Revenue Service. IRS tax relief announcement, Washington disaster
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Electronic Federal Tax Payment System. Electronic Federal Tax Payment System
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Internal Revenue Service. Same-Day Wire Federal Tax Payments
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Electronic Federal Tax Payment System. Same-Day Wire Taxpayer Worksheet
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Internal Revenue Service. Instructions for Form 2220
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Office of the Law Revision Counsel. 26 U.S. Code 6655
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Internal Revenue Service. 2025 Instructions for Form 2220
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Internal Revenue Service. Underpayment of Estimated Tax by Corporations Penalty
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Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 2026
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Internal Revenue Service. Form 2220
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Internal Revenue Service. Instructions for Form 1120 (2025)