Iowa Code § 123.93

Within six months of the occurrence of an injury, the injured person shall give written notice to the licensee or permittee or such licensee’s or permittee’s insurance carrier of the person’s intention to bring an action under this section, indicating the time, place and circumstances causing the injury. Such six months’ period shall be extended if the injured party is incapacitated at the expiration thereof or unable, through reasonable diligence, to discover the name of the licensee, permittee, or person causing the injury or until such time as such incapacity is removed or such person has had a reasonable time to discover the name of the licensee, permittee or person causing the injury.