For each independent contractor and exempt person hired, an employer shall retain the following records at the work site or at its place of business: A statement with a description of the employer's usual course of business or a fully executed copy of the contract between the employer and the independent contractor or exempt person; Acknowledgement forms signed by the independent contractor and exempt person; and Licenses or registrations provided by an individual classified as an independent contractor or exempt person. An employer shall retain each record for 3 years.