Spurlock v. State Fund [7/15/03] 2003 MTWCC 49 A certificate of insurance which certifies there is workers' compensation insurance coverage for a business operated by a sole proprietor but which also warns the reader that certain employees may opt out does not estop the insurer from denying coverage to a sole proprietor who has expressly opted not to have coverage for himself or herself. There is no estoppel since there is no misrepresentation of fact.