A "private company" is any company that is not a public company.
A "public company" is a company limited by shares or limited by guarantee and having a share capital—
whose certificate of incorporation states that it is a public company, and
in relation to which the requirements of this Act, or the former Companies Acts, as to registration or re-registration as a public company have been complied with on or after the relevant date.
For the purposes of subsection (2)(b) the relevant date is—
in relation to registration or re-registration in Great Britain, 22nd December 1980;
in relation to registration or re-registration in Northern Ireland, 1st July 1983.
For the two major differences between private and public companies, see Part 20.