805 ILCS 10/9
A professional corporation shall adopt a name consisting of the full or last name of one or more of its shareholders; except that if not otherwise prohibited by law, rules of a regulating authority or the canons of ethics of the profession concerned, a professional corporation may adopt a fictitious name. If the corporation does adopt a fictitious name or continues to use the name of a deceased shareholder, the name of a member of a predecessor organization, it shall file with the county clerk of the county where its principal place of business is located, under "An Act in relation to the use of an assumed name in the conduct or transaction of business in this State," approved July 17, 1941, as now or hereafter amended. It shall be permissible for a professional corporation to continue to use the name of a deceased shareholder for a period of one year after his death without recording the name of the corporation with the county clerk as hereinabove provided. A professional corporation may continue to use the name of a shareholder who voluntarily withdraws from the corporation if the withdrawing shareholder files with the regulating authority his written permission for the continued use of his name by the professional corporation. This permission shall remain in effect until written revocation has been received by the regulating authority from the former shareholder.
The corporate name shall end with the word "chartered" or "Limited" or the abbreviation "Ltd.", or with the words "Professional Corporation" or the abbreviation "Prof. Corp." or the initials "P. C.".
805 ILCS 10/9