38 C.F.R. § 21.282
Effective date of induction into a rehabilitation program; retroactive induction
(a) Entering a rehabilitation program. The effective date of induction into a rehabilitation program is governed by the provisions of §§ 21.320 through 21.334, except as provided in this section.
(b) Retroactive induction. Subject to paragraphs (c) and (d) of this section, an individual may be inducted into a rehabilitation program on a retroactive basis. If the individual is retroactively inducted, VA may authorize payment pursuant to § 21.262 or § 21.264 for tuition, fees, and other verifiable expenses that an individual paid or incurred consistent with the approved rehabilitation program. In addition, VA may authorize payment of subsistence allowance pursuant to §§ 21.260, 21.266, and 21.270 for the period of retroactive induction, except for any period during which the individual was on active duty.
(c) Conditions for retroactive induction. Retroactive induction into a rehabilitation program may be authorized for a past period under a claim for vocational rehabilitation benefits when all of the following conditions are met:
(1) The past period is within—
(i) A period under § 21.40(c) during which a servicemember was awaiting discharge for disability; or
(ii) A period of eligibility under §§ 21.41 through 21.44 or 38 U.S.C. 3103.
(2) The individual was entitled to disability compensation under 38 U.S.C. chapter 11 during the period or would likely have been entitled to that compensation but for active-duty service.
(3) The individual met the criteria for entitlement to vocational rehabilitation benefits and services under 38 U.S.C. chapter 31 in effect during the period.
(4) VA determines that the individual's training and other rehabilitation services received during the period were reasonably needed to achieve the goals and objectives identified for the individual and may be included in the plan developed for the individual (see §§ 21.80 through 21.88, and §§ 21.92 through 21.96).
(5) VA has recouped any benefits that it paid the individual for education or training pursued under any VA education program during any portion of the period.
(6) An initial evaluation was completed under § 21.50.
(7) A period of extended evaluation is not needed to be able to determine the reasonable feasibility of the achievement of a vocational goal.
(d) Effective date for retroactive induction. The effective date for retroactive induction is the date when all the entitlement conditions set forth in paragraph (c) of this section are met, and for a veteran (except as to a period prior to discharge from active duty) in no event before the effective date of a VA rating under 38 U.S.C. chapter 11 establishing a qualifying level under § 21.40 of service-connected disability.