S Corp Tax Deadlines: The Quarterly Rhythm Every Owner Should Run

Why an S Corp runs on a calendar

An S corporation election changes more than a tax form. The owner who works in the business becomes its employee, and wages paid to an employee come with deposits, quarterly returns, and year end forms. None of it is complicated. Each piece simply has its own clock, and the clocks do not line up.

Four events repeat every year: payroll tax deposits, Form 941 each quarter, the owner's personal estimated tax, and the Form 1120-S return. Run them as a rhythm and nothing arrives as a surprise.

The dates below are the general federal rules for a calendar year S corporation. When a due date lands on a Saturday, Sunday, or legal holiday, the IRS moves it to the next business day. State payroll and income tax agencies keep their own calendars, so confirm those separately.

Event one: payroll tax deposits

Every paycheck to the owner carries withheld federal income tax, Social Security tax, and Medicare tax, and the corporation owes its own share of Social Security and Medicare on top. That money is deposited with the IRS electronically, through a business tax account, Direct Pay for businesses, or the Electronic Federal Tax Payment System.

Every employer falls under one of two deposit schedules, set before each calendar year from the taxes reported during a lookback period that runs from July 1 to June 30. A business that reported $50,000 or less is a monthly schedule depositor. A business that reported more is a semiweekly schedule depositor. A new employer filing Form 941 is treated as having no prior liability, so it is a monthly schedule depositor for its first calendar year.

A monthly schedule depositor deposits the taxes on wages paid during a month by the 15th day of the following month. A semiweekly schedule depositor deposits by the following Wednesday for paydays that fall on Wednesday, Thursday, or Friday, and by the following Friday for paydays that fall on Saturday through Tuesday. A business that accumulates $100,000 or more of tax on any day must deposit by the next business day.

A payroll provider usually makes these deposits. The owner's job is to confirm each one went out and that the account had the funds. This matters personally, because the trust fund recovery penalty can reach the people responsible for withheld taxes that were never paid over.

Event two: Form 941, four times a year

Form 941 reports the wages paid and the taxes withheld and deposited for each quarter. It is due by the last day of the month after the quarter ends: April 30, July 31, October 31, and January 31. If every deposit for the quarter was made on time, the IRS allows 10 additional calendar days to file.

January is the heavy month. Along with the fourth quarter Form 941, the business files Forms W-2 with Form W-3 by January 31 and gives the owner and any other employee a Form W-2 by the same date. Form 940, the federal unemployment return, is also due January 31. A business that paid contractors files Form 1099-NEC by January 31 as well.

Federal unemployment tax has its own deposit rule. A liability of $500 or less for a quarter carries forward. Once the running total passes $500, the deposit is due by the last day of the month after the quarter ends.

The four Forms 941 should add up to the Form W-3 totals. The IRS and the Social Security Administration compare the two, and a mismatch produces a notice. The same wage total should appear on Form 1120-S.

Event three: the owner's estimated tax

An S corporation generally does not pay federal income tax itself. Its profit passes through to the owner's personal return, whether or not the cash was distributed. Withholding on the owner's wages covers the tax on those wages. It does not automatically cover the tax on the profit that passes through.

The IRS says individuals, including S corporation shareholders, generally have to make estimated tax payments if they expect to owe $1,000 or more when the return is filed. The four payments for a calendar year are due April 15, June 15, September 15, and January 15 of the following year.

There is a second route. An owner who is on payroll can ask the corporation to withhold more federal income tax from each paycheck, using the extra withholding line on Form W-4. Many owners prefer this, because the tax leaves with payroll instead of waiting for a quarterly date.

The underpayment penalty is generally avoided when less than $1,000 is owed after withholding and credits, or when payments reached at least 90 percent of the current year tax or 100 percent of the prior year tax, whichever is smaller. A higher prior year percentage applies at higher incomes. Publication 505 has the detail.

The corporation makes its own estimated payments only in narrow cases. The Form 1120-S instructions limit them to the tax on built in gains, the excess net passive income tax, and investment credit recapture, and only when those total $500 or more.

Event four: Form 1120-S and the Schedule K-1

Form 1120-S is due by the 15th day of the third month after the tax year ends. For a calendar year corporation that is March 15. The 2026 return is due Monday, March 15, 2027. Form 7004 requests an automatic extension of time to file, and it has to be filed by the regular due date.

The return produces a Schedule K-1 for each shareholder. The owner cannot finish a personal return without it, which is why the corporate return comes a month before the personal deadline.

Late filing is expensive even when no tax is due. Under the 2025 Form 1120-S instructions the penalty is $255 for each month or part of a month the return is late, for up to 12 months, multiplied by the number of shareholders. A separate $340 penalty can apply for each Schedule K-1 that is not furnished on time. The IRS adjusts these amounts, so check the instructions for the year being filed.

March 15 carries one more deadline. A calendar year business that wants S corporation status to start January 1 generally has to file Form 2553 within two months and 15 days of the start of the tax year, which also lands on March 15.

The year on one page

January 15: fourth quarter estimated tax for the prior year. January 31: Form 941 for the fourth quarter, Forms W-2 and W-3, Form 940, and Form 1099-NEC.

March 15: Form 1120-S or Form 7004, Schedules K-1 to shareholders, and Form 2553 for a new election.

April 15: first quarter estimated tax and the personal return. April 30: Form 941 for the first quarter.

June 15: second quarter estimated tax. July 31: Form 941 for the second quarter.

September 15: third quarter estimated tax. October 31: Form 941 for the third quarter.

Every month by the 15th: the prior month's payroll tax deposit, for a monthly schedule depositor.

Where owners slip

Payroll starts late. The election is effective January 1, but the first paycheck does not run until the fall. Wages still have to reflect the work done during the year, and a compressed payroll makes the deposit and Form 941 timing harder to keep clean.

Distributions go out with no wages behind them. The IRS expects a shareholder who works in the business to be paid reasonable compensation before taking distributions. Distributions paid while the Forms 941 report no wages is a pattern that invites questions.

The state side is forgotten. State withholding, state unemployment tax, and in some states a separate entity return or election each run on their own dates.

The estimated tax plan is built on last year. Profit that grows after the election changes the income that passes through. Revisit the plan when the midyear numbers are in.