In order to qualify for S corporation status, a corporation must meet the following requirements: It must be a domestic corporation; it must have only certain types of shareholders (such as individuals, certain types of trusts, and estates, but not partnerships, corporations, or non-resident aliens); it must have no more than 100 shareholders; it must have only one class of stock; and it must not be what the IRS calls an ineligible corporation, including certain types of financial institutions, insurance companies, and domestic international sales corporations.