38 CFR § 3.321 - General rating considerations.
(a) Use of rating schedule. The 1945 Schedule for Rating Disabilities will be used for evaluating the degree of disabilities in claims for disability compensation, disability and death pension, and in eligibility determinations. The provisions contained in the rating schedule will represent as far as can practicably be determined, the average impairment in earning capacity in civil occupations resulting from disability.
(b) Extra-schedular ratings in unusual cases—(1) Disability compensation. Ratings shall be based, as far as practicable, upon the average impairments of earning capacity with the additional proviso that the Secretary shall from time to time readjust this schedule of ratings in accordance with experience. To accord justice to the exceptional case where the schedular evaluation is inadequate to rate a single service-connected disability, the Director of Compensation Service or his or her delegate is authorized to approve on the basis of the criteria set forth in this paragraph (b), an extra-schedular evaluation commensurate with the average impairment of earning capacity due exclusively to the disability. The governing norm in these exceptional cases is a finding by the Director of Compensation Service or delegatee that application of the regular schedular standards is impractical because the disability is so exceptional or unusual due to such related factors as marked interference with employment or frequent periods of hospitalization.
(2) Pension. Where the evidence of record establishes that an applicant for pension who is basically eligible fails to meet the disability requirements based on the percentage standards of the rating schedule but is found to be unemployable by reason of his or her disability(ies), age, occupational background and other related factors, the following are authorized to approve on an extra-schedular basis a permanent and total disability rating for pension purposes: the Veterans Service Center Manager or the Pension Management Center Manager; or where regular schedular standards are met as of the date of the rating decision, the rating board.
(3) Effective dates. The effective date of these extra-schedular evaluations granting or increasing benefits will be in accordance with § 3.400(b)(1) and (2) as to original and supplemental claims and in accordance with § 3.400(o) in claims for increased benefits.
(c) Advisory opinion. Cases in which application of the schedule is not understood or the propriety of an extra-schedular rating is questionable may be submitted to Central Office for advisory opinion.