Form 1120-W is the IRS worksheet corporations use to calculate quarterly estimated federal income tax payments. It isn’t filed with the IRS; it’s a working document that walks you through figuring the required annual payment, splitting it into four installments, and comparing methods to arrive at the lowest legal payment for each quarter. Any C corporation expecting to owe $500 or more in federal tax for the year needs to work through it and pay on schedule, because interest runs on any shortfall from the moment an installment comes due.
Who Needs to Use the Worksheet
The trigger is simple. If a corporation’s total federal tax for the year will be $500 or more after credits, it must make quarterly estimated payments. That number comes directly from the penalty exception in the tax code: when the tax on the return is under $500, no underpayment penalty applies regardless of whether the corporation paid estimates.1Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax
To test the threshold, add expected regular income tax and any alternative minimum tax, then subtract anticipated credits. Compare the net figure to $500. New corporations without a prior-year return still estimate from scratch and begin paying if they expect to cross the line.
S corporations, partnerships, and most tax-exempt organizations use different rules and different forms; 1120-W is for corporations filing Form 1120.
Figuring the Required Annual Payment
The worksheet’s central calculation is the “required annual payment” — the total that must be paid across four installments to avoid a penalty. By statute, this amount is the lesser of two figures: 100 percent of the tax shown on the current year’s return, or 100 percent of the tax shown on the prior year’s return.1Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax
The prior-year option only works if the previous return covered a full 12-month tax year and showed at least some tax liability. If last year was a short period or the corporation owed zero, current-year projections are the only path.
Each quarterly installment is generally 25 percent of the required annual payment. Required annual payment of $200,000 means four installments of $50,000. The worksheet lets you compare methods and take the lowest permissible payment for each quarter separately, so you don’t have to commit to one approach for the whole year.
The Four Calculation Methods
The tax code recognizes four ways to size each installment. Whichever produces the lowest legal payment for a given quarter is the one you can use.
Standard Current-Year Method
Estimate the full-year tax liability and divide by four. Each installment is 25 percent of the current year’s expected tax. This is the default for corporations with steady, predictable income.
Prior-Year Safe Harbor
Pay 25 percent of last year’s total tax each quarter, based on the safe harbor at 100 percent of prior-year tax.1Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax This gives certainty before you know how the current year will land. It only works if last year was a full 12 months and showed positive tax, and it’s restricted for large corporations (see below).
Annualized Income Installment Method
Corporations with uneven income can match payments to when income is actually earned. Instead of dividing evenly, each installment is based on income through a specific cutoff, then annualized to figure the tax for that installment.
Default periods: the first and second installments look at the first 3 months, the third uses the first 6 months, the fourth uses the first 9 months. A corporation can elect alternative measurement periods of 2-4-7-10 or 3-5-8-11 months if those better reflect its earnings pattern.1Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax The election must be made by the first installment due date and applies for the whole year.
One thing to understand: reducing an earlier installment under this method just shifts the money to a later installment. You defer, you don’t eliminate.
Adjusted Seasonal Installment Method
Narrower than the annualized approach. Available only when at least 70 percent of taxable income falls within any six consecutive months of the year, and only for corporations with a stable seasonal history.1Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax Each installment is calculated using the average share of income earned in those same months across the previous three tax years. A resort earning most of its revenue May through October would base installments on that historical pattern rather than assuming income arrives evenly.
Large Corporation Rules
A “large corporation” for this purpose is one that had taxable income of $1 million or more in any of the three preceding tax years, ignoring net operating loss carrybacks and capital loss carryovers.1Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax Predecessor corporations count, and controlled group members share the $1 million threshold.
The important restriction: a large corporation can use the prior-year safe harbor only for the first installment. Every installment after that must be based on the current year’s estimated tax.1Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax Any reduction taken in the first installment from using last year’s numbers gets added to the second installment. So for large corporations, the prior-year option doesn’t reduce total payments; it only affects the timing of the first two.
Installment Due Dates
Calendar-year corporations pay on this schedule:
- First installment: April 15
- Second installment: June 15
- Third installment: September 15
- Fourth installment: December 15
Fiscal-year corporations follow the same pattern using the 15th day of the 4th, 6th, 9th, and 12th months of their fiscal year.1Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax When any due date falls on a weekend or legal holiday, the deadline shifts to the next business day.2Internal Revenue Service. Topic No. 301 When, How and Where to File
The gaps aren’t even. Two months between the first and second payments, then three months to the third, then three more to the fourth. Corporations with tight cash flow sometimes get caught by the short April-to-June window.
How to Submit the Payments
The IRS accepts corporate estimated payments through three channels.
EFTPS. The Electronic Federal Tax Payment System is the standard method. Payments can be scheduled up to 365 days ahead, and you get immediate confirmation on submission.3Internal Revenue Service. EFTPS: The Electronic Federal Tax Payment System Enrollment requires the corporation’s EIN and a PIN, and funds transfer from the corporate bank account on the date you choose.
Same-day wire. For last-minute payments, a corporation can wire funds through its bank using the IRS Same-Day Taxpayer Worksheet, with a separate worksheet for each tax form and period.4Internal Revenue Service. Same-Day Wire Federal Tax Payments Not every bank offers the service, and those that do usually charge a fee.
Check or money order. Still permitted, mailed with a payment voucher. The mailing address depends on the state where the corporation is headquartered; the form instructions list current addresses. The postmark date counts as the payment date.
What CAMT Filers Should Know
The corporate alternative minimum tax applies to corporations with average annual adjusted financial statement income above $1 billion, and it creates its own estimated tax obligation. For tax years beginning before January 1, 2026, the IRS waived underpayment penalties tied to CAMT liability while regulations were being developed.5Internal Revenue Service. Notice 2025-27 – Waiver of Certain Additions to Tax under Section 6655 That waiver does not extend to 2026 tax years.
For 2026 forward, applicable corporations need to fold projected CAMT liability into their 1120-W calculations. Leaving it out will create an underpayment subject to the standard penalty interest.
What Happens If You Underpay
When a corporation underpays an installment, the IRS charges interest on the shortfall from the installment due date until the payment is made or the return is due, whichever comes first. The charge is calculated at the federal short-term rate plus 3 percentage points, compounded daily, and adjusts quarterly.6Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 2026 Large corporate underpayments carry a higher rate.7Internal Revenue Service. Internal Revenue Bulletin 2026-08
Corporations use Form 2220 with the annual return to figure whether a penalty applies and how much.8Internal Revenue Service. About Form 2220, Underpayment of Estimated Tax By Corporations No penalty applies if total tax on the return is under $500. Using the annualized income or adjusted seasonal methods on Form 2220 can also reduce or eliminate the penalty for quarters when income hadn’t yet materialized.9Internal Revenue Service. Instructions for Form 2220
If You Overpay
Corporations that pay in more than they end up owing can get a fast refund using Form 4466 rather than waiting for the annual return to process. The overpayment has to be at least $500 and at least 10 percent of expected tax liability for the year.10Internal Revenue Service. About Form 4466, Corporation Application for Quick Refund of Overpayment of Estimated Tax
The window is narrow. Form 4466 must be filed after the tax year ends but before the return’s original due date, and before the return itself is filed. Filing extensions don’t extend the 4466 deadline.11Internal Revenue Service. Instructions for Form 4466 For a calendar-year corporation, that means getting Form 4466 in by April 15 and before filing the Form 1120. The IRS has 45 days to act on the application once received.