There is also a sub-set of private investors: people who become shareholders in quoted companies by virtue of being shareholder employees of a company that goes through flotation; by holding performance-related share options; or by purchasing shares via company-sponsored schemes. In all cases, these shares may, ultimately, become ordinary (tradable) shares, although companies may impose restrictions on when shares can be bought or sold. Unusually, the UK offers companies and private investors a range of tax-efficient investment opportunities. These include investments made in shares of companies quoted on AIM; in Venture Capital Trusts (VCTs); in Enterprise Investment Scheme–qualifying (EIS).