S Corp IRS Rules: Election, Taxes, and Annual Filing

The IRS rules for S corporations set who can elect the status, how the election is made, how income and losses flow to shareholders, and what the corporation must file each year. An S corp itself generally pays no federal income tax; profits, losses, deductions, and credits pass through to shareholders and are taxed on their individual returns.¹ In exchange for that single layer of tax, the corporation must meet the eligibility rules in Section 1361 of the Internal Revenue Code, file its election on time, pay working owners a reasonable salary, and stay compliant every year the status is in effect.

Who Qualifies as an S Corporation

The IRS grants S corp status only to a “small business corporation” that satisfies every requirement in Section 1361. Miss one, and the election either fails or terminates automatically.

The entity must be a domestic corporation.
It cannot have more than 100 shareholders. Members of an extended family, defined as a common ancestor plus all lineal descendants and their spouses, count as a single shareholder.²
Owners must be U.S. citizens or resident alien individuals, certain trusts, or estates. Partnerships, other corporations, and nonresident aliens cannot hold shares.¹
The corporation can issue only one class of stock, although shares may differ in voting rights.²
Certain financial institutions, insurance companies, and domestic international sales corporations are ineligible even if they meet everything else.¹

If the corporation falls out of compliance during any year, the election ends automatically and the entity reverts to C corp taxation. Getting the status back generally requires waiting five years unless the IRS consents to an earlier re-election.

Making the Election

A corporation elects S status by filing IRS Form 2553. Every shareholder who owns stock on the day of the election must sign the form or provide a written consent statement. The filing must arrive either during the preceding tax year or no later than the 15th day of the third month of the tax year the election is meant to cover. For a calendar-year corporation, that deadline is March 15.³

If eligibility was met on the filing date but a shareholder had not yet consented, or the form arrived a few days late, the election rolls forward to the following tax year rather than being rejected.

Late Election Relief

A business that missed the deadline entirely can still request retroactive S status under Revenue Procedure 2013-30, provided the request is made within three years and 75 days of the intended effective date. The IRS requires reasonable cause for the delay. One commonly accepted reason is reliance on a tax professional who failed to file the election or advise that it was necessary.⁴ The corporation must also have reported its income consistently as an S corp for the entire period covered by the retroactive request.

How S Corp Income Is Taxed

Each shareholder reports a pro rata share of the corporation’s income, losses, deductions, and credits on their individual return, whether or not the corporation actually distributed any cash.⁵ The character of each item survives the pass-through: capital gains stay capital gains, ordinary income stays ordinary. Shareholders pay at their personal rates, and the corporation itself owes no federal income tax on that income.

Reasonable Compensation for Working Owners

A shareholder who also works for the S corp must be paid a salary that qualifies as reasonable compensation for the services they actually perform. The IRS treats corporate officers who render services as employees by definition, and their pay is subject to income tax withholding, Social Security tax, and Medicare tax like any other employee’s wages.⁶

Combined FICA runs 15.3%: 12.4% for Social Security (split between the corporation and the employee) up to the annual wage base, plus 2.9% for Medicare with no cap.⁷ Distributions paid on top of a reasonable salary are not subject to employment taxes, and that gap is the main payroll-tax advantage of the S corp structure.

It’s also the biggest audit target. A shareholder drawing a $40,000 salary while taking $300,000 in distributions and performing full-time executive duties will attract attention. If the IRS decides the salary was too low, it can reclassify distributions as wages and assess back employment taxes, interest, and penalties against the corporation.⁶ There is no bright-line safe harbor. Courts weigh comparable industry pay, the shareholder’s qualifications, hours worked, and the corporation’s revenue.

Health Insurance for More-Than-2% Shareholders

When the S corp pays health insurance premiums for a shareholder who owns more than 2% of the stock, the premiums are deductible by the corporation but must be reported as wages on that shareholder’s W-2.⁸ Those premium amounts escape Social Security, Medicare, and federal unemployment tax. The shareholder can then take an above-the-line deduction on the personal return for the same amount, which usually zeroes out the income tax effect.

That above-the-line deduction disappears if the shareholder or their spouse could have participated in a subsidized health plan through another employer. More-than-2% shareholders are also barred from participating in flexible spending arrangements, health reimbursement arrangements, and qualified small employer health reimbursement arrangements.⁸

Section 199A Deduction

S corp shareholders may qualify for the Section 199A deduction of up to 20% of qualified business income. The deduction was originally set to expire after 2025 but was made permanent by the One Big Beautiful Bill Act. It is taken on the shareholder’s individual return, not at the corporate level. Above certain income thresholds the deduction phases out for specified service trades such as law, medicine, and consulting, and a separate wage-and-capital limitation applies to all businesses.

Basis Limits on Losses

A shareholder can only deduct S corp losses up to their basis. Basis starts with the amount paid for the stock or contributed as capital, then adjusts each year: income items raise it, and losses, deductions, and non-dividend distributions lower it.⁹ Basis can never drop below zero.

If losses exceed stock basis, the shareholder can deduct the excess up to their debt basis. Debt basis comes only from money the shareholder has personally lent to the corporation. Guaranteeing a bank loan is not enough; the shareholder must be the actual creditor.⁹ Co-signing on a $500,000 line of credit produces zero debt basis unless the shareholder actually funds the loan.

Losses that exceed both stock and debt basis are not lost. They carry forward indefinitely and become deductible in any future year when basis is restored through capital contributions, additional shareholder loans, or allocated income.⁹ Suspended losses keep their original character, so an ordinary loss stays ordinary when it finally becomes usable. Selling the stock before using the suspended losses, though, wipes them out permanently.

Annual Filing and Reporting

An S corporation files Form 1120-S each year to report income, gains, losses, deductions, and credits. Calendar-year corporations must file by March 15. The corporation must also issue a Schedule K-1 to each shareholder by the same date, breaking out that owner’s share of every line on the corporate return.¹⁰ Each shareholder then uses the K-1 to complete the corresponding sections of their Form 1040.

Filing Form 7004 before the March 15 deadline grants an automatic six-month extension, moving the due date to September 15.¹¹ The extension covers filing only, not payment of any tax the corporation owes.

Estimated Tax Payments

Because income passes through, the IRS expects each shareholder to make quarterly estimated tax payments on their share. For calendar-year taxpayers, those payments are due April 15, June 15, September 15, and January 15 of the following year.¹² Shareholders who are also W-2 employees of the S corp can often skip the quarterly process by increasing salary withholding instead.

Late Filing Penalty

The penalty for filing Form 1120-S late is $255 per shareholder for each month or partial month the return is overdue, up to 12 months.¹³ A five-owner S corp that files four months late owes $5,100. The penalty applies even when the corporation owes no tax, which catches many owners off guard. Filing Form 7004 before the deadline avoids it.

Extra Taxes for Former C Corporations

S corporations that converted from C corp status can owe two entity-level taxes that never apply to businesses formed as S corps from the start. Both exist to keep companies from stockpiling gains or passive income under C corp rates and then converting to shed the second layer of tax.

Built-in Gains Tax

Appreciation that existed in the corporation’s assets on the day of conversion is subject to a built-in gains tax if those assets are sold within five years of the S election.¹⁴ The rate is 21%, matching the corporate income tax rate. After the five-year recognition period, the assets can be sold without this extra tax. Appreciation that occurred after the S election is never subject to it.

Excess Passive Investment Income Tax

An S corporation that still carries accumulated earnings and profits from its C corp years owes a special tax when more than 25% of its gross receipts come from passive sources like interest, dividends, rents, and royalties.¹⁵ The tax hits the excess net passive income at 21%. More importantly, if the 25% threshold is exceeded for three consecutive years while C corp earnings and profits remain, the S election terminates automatically at the start of the fourth year.³ Distributing the accumulated C corp earnings before the three-year mark is the usual defense.

How the Election Ends

An S election stays in effect until it is voluntarily revoked or involuntarily terminated.

Shareholders owning more than 50% of the stock can revoke the election by filing a statement with the IRS. A revocation filed by the 15th day of the third month of the tax year takes effect that year; filed later, it takes effect the following year unless a future date is specified.³
If the corporation stops qualifying as a small business corporation under Section 1361, the election terminates on the day of the disqualifying event. Admitting a corporate shareholder or crossing the 100-shareholder limit would do it.
Three consecutive years of passive investment income above 25% of gross receipts, combined with lingering C corp earnings and profits, ends the election at the start of the fourth year.³

If a termination was inadvertent, such as an ownership transfer that accidentally routed shares to an ineligible shareholder, the IRS can grant relief and treat the election as if it never ended. The corporation must fix the disqualifying event and show the termination was not part of a deliberate plan.⁴ After a revocation or termination, the corporation generally cannot re-elect S status for five years without IRS consent.

1
Internal Revenue Service. S Corporations
2
Office of the Law Revision Counsel. 26 U.S. Code 1361 – S Corporation Defined
3
Office of the Law Revision Counsel. 26 U.S. Code 1362 – Election; Revocation; Termination
4
Internal Revenue Service. Revenue Procedure 2013-30
5
Office of the Law Revision Counsel. 26 U.S. Code 1366 – Pass-Thru of Items to Shareholders
6
Internal Revenue Service. Wage Compensation for S Corporation Officers FS-2008-25
7
Social Security Administration. Contribution and Benefit Base
8
Internal Revenue Service. S Corporation Compensation and Medical Insurance Issues
9
Internal Revenue Service. S Corporation Stock and Debt Basis
10
Internal Revenue Service. About Form 1120-S, U.S. Income Tax Return for an S Corporation
11
Internal Revenue Service. Instructions for Form 7004 (12/2025)
12
Internal Revenue Service. Publication 509 (2026), Tax Calendars
13
Internal Revenue Service. Failure to File Penalty
14
Office of the Law Revision Counsel. 26 USC 1374 – Tax Imposed on Certain Built-In Gains
15
eCFR. 26 CFR 1.1375-1 – Tax Imposed When Passive Investment Income of Corporation Having Subchapter C Earnings and Profits Exceed 25 Percent of Gross Receipts