38 C.F.R. § 3.401
Awards of pension or compensation payable to or for a veteran will be effective as follows:
(a) Aid and attendance and housebound benefits.
(1) Except as provided in § 3.400(o)(2), the date of receipt of claim or date entitlement arose, whichever is later. However, when an award of pension or compensation based on an original or supplemental claim is effective for a period prior to the date of receipt of the claim, any additional pension or compensation payable by reason of need for aid and attendance or housebound status shall also be awarded for any part of the award's retroactive period for which entitlement to the additional benefit is established.
(Authority: 38 U.S.C. 501; 5110(b)(1), (3))
(2) Date of departure from hospital, institution, or domiciliary.
(Authority: 38 U.S.C. 501)
(3) Spouse, additional compensation for aid and attendance: Date of receipt of claim or date entitlement arose, whichever is later. However, when an award of disability compensation based on an original or supplemental claim is effective for a period prior to date of receipt of the claim additional disability compensation payable to a veteran by reason of the veteran's spouse's need for aid and attendance shall also be awarded for any part of the award's retroactive period for which the spouse's entitlement to aid and attendance is established.
(Authority: 38 U.S.C. 501; 5110(b)(1), (2))
(b) Dependent, additional compensation or pension for. Latest of the following dates:
(1) Date of claim. This term means the following, listed in their order of applicability:
(3) Effective date of the qualifying disability rating provided evidence of dependency is received within 1 year of notification of such rating action.
(Authority: 38 U.S.C. 5110(f))
(4) Date of commencement of veteran's award. (Other increases, see § 3.400(o). For school attendance see § 3.667.)
(Authority: 38 U.S.C. 5110 (f), (n))
(2) Section 4.30 of this chapter. Date of entrance into hospital, after discharge from hospitalization (regular or release to non-bed care).
[26 FR 1594, Feb. 24, 1961, as amended at 27 FR 11889, Dec. 1, 1962; 36 FR 4599, Mar. 10, 1971; 39 FR 17222, Mar. 14, 1974; 41 FR 36493, Aug. 30, 1976; 41 FR 55874, Dec. 23, 1976; 41 FR 56804, Dec. 30, 1976; 45 FR 34886, May 23, 1980; 54 FR 34981, Aug. 23, 1989; 62 FR 5529, Feb. 6, 1997; 83 FR 32738, July 13, 2018; 84 FR 170, Jan. 18, 2019]