S-Corp Eligibility Requirements: The 100-Shareholder Cap, One Class of Stock, and Who Can Own Shares

Picture a two-founder software LLC that elected S-Corp status last year. Now a venture fund wants to buy in, one of the founders has moved abroad and given up her green card, and the team wants to hand an early engineer a slice of preferred stock that pays out first in a sale. Each of those three moves, on its own, ends the S election the moment it closes. The founders here are theoretical, not EntityIQ clients, but the trap is real and I see versions of it constantly. The rules that govern all three sit in one place, IRC §1361.

What the tax code means by a "small business corporation"

A corporation qualifies as a small business corporation, and can hold an S election, only if it is a domestic corporation, has no more than 100 shareholders, has only eligible shareholders, has no nonresident alien as a shareholder, and has no more than one class of stock. Those five tests come straight from §1361(b)(1). Miss any one and the election either never takes effect or terminates. An LLC that files Form 2553 has to clear the same five tests as any corporation, because the election treats the LLC as a corporation for federal tax purposes. The LLC label does not buy you out of a single requirement below.

The 100-shareholder cap, and the family exception

Section 1361(b)(1)(A) sets the ceiling at 100 shareholders. Most small businesses never come close, but the count matters for family businesses and companies that hand out equity widely. Section 1361(c)(1) softens the cap: all members of a family count as a single shareholder. Members of a family means a common ancestor, that ancestor's lineal descendants, and the spouses or former spouses of any of them. The common ancestor cannot be more than six generations removed from the youngest family shareholder, measured on the applicable date, which is the latest of the election's effective date, the date a family member first acquired stock, or October 22, 2004. The common ancestor never has to have owned a share, and does not even have to be alive.

Who is allowed to hold the stock

Eligible shareholders are a short list. Individuals who are US citizens or resident aliens, estates, certain trusts, and a narrow set of tax-exempt organizations. Under §1361(c)(6), the only exempt owners allowed are qualified retirement plan trusts under §401(a) and charities under §501(c)(3). The trusts that qualify are set out in §1361(c)(2): grantor trusts, testamentary trusts for a two-year window, voting trusts, the qualified subchapter S trust (QSST) under §1361(d), and the electing small business trust (ESBT) under §1361(e).

Who cannot own shares is the part that trips people up. A partnership cannot be a shareholder. A corporation cannot be a shareholder. That means a multi-member LLC, which the IRS treats as a partnership by default, cannot hold S-Corp stock, and neither can a venture fund organized as an LP or LLC. A nonresident alien cannot be a shareholder, which is why a founder who gives up US residency ends the election. One narrow post-2017 wrinkle: a nonresident alien can be a potential current beneficiary of an electing small business trust under §1361(c)(2)(B)(v), but that is a beneficiary of a qualifying trust, not a direct shareholder.

One class of stock, and why preferred equity breaks it

Section 1361(b)(1)(D) allows only one class of stock. Treasury Regulation §1.1361-1(l) says a corporation has one class of stock if all outstanding shares confer identical rights to distribution and liquidation proceeds. Differences in voting rights are fine, so you can have voting and nonvoting common stock. What you cannot have is a share that pays out first or pays a fixed preferred return, because that is a second class of stock. That is why handing an employee preferred stock ends the election, and why LLC operating agreements are a quiet danger. A special allocation or a preferred return written into the operating agreement can be read as a second class of stock even when the cap table looks clean. The regulation tests the governing documents, not a single accidental distribution, but bona fide loans still matter here: debt that meets the straight-debt safe harbor in §1361(c)(5) is not treated as a second class of stock.

The corporations that can never elect

Even a company that clears the shareholder and stock tests can be barred by what it does. Section 1361(b)(2) lists ineligible corporations: a bank or thrift that uses the reserve method of accounting for bad debts under §585, an insurance company taxed under subchapter L, a corporation that has elected the Puerto Rico and possessions tax credit under §936, and a current or former domestic international sales corporation (DISC). Most service and product businesses never touch this list, but it is worth a glance if you are in banking or insurance.

What happens if you break a rule

An S election that fails a test terminates on the date of the disqualifying event, and the company reverts to C-Corp taxation for the rest of the year and beyond. If the violation was inadvertent, §1362(f) lets you ask the IRS for relief and reinstatement, usually through a private letter ruling, but that costs time and money. It is cheaper to check the five boxes before you sign a term sheet, add a foreign owner, or print a stock certificate. Before you bring in outside money or restructure the cap table, run the change past these eligibility rules first. And if you are still deciding whether the election is even worth it, the EntityIQ calculator and our S-Corp or LLC comparison show what an S-Corp saves before you worry about who can own it.

This article is educational and is not legal or tax advice. The founders described above are theoretical, and the rules are the 2026 versions of §1361. Please consult a qualified CPA or attorney before you change your ownership structure or file an S-Corp election.