Idaho Code § 72-703

Any notice under this law shall be given to the employer, or, if the employer is a partnership, then to any one (1) of the partners. If the employer is a corporation, then the notice may be given to any agent of the corporation upon whom process may be served, or to any officer of the corporation, or any agent in charge of the business at the place where the injury occurred. Such notice shall be given by delivering it or by sending it by registered or certified mail addressed to the employer at his or its last known residence or place of business. The foregoing provisions shall apply to the making of a claim.