To be considered a preference eligible, the person must submit with the employment application a Bureau of Indian Affairs certification that the person is an Indian as defined by § 136.41 except that an employee of the Indian Health Service who has a certificate of preference eligibility on file in the Official Personnel Folder is not required to resubmit such proof but may instead include a statement on the application that proof of eligibility is on file in the Official Personnel Folder.
42 C.F.R. §136.43