38 CFR § 17.126 - Timely filing.
Claims for payment or reimbursement of the expenses of medical care or services not previously authorized must be filed within the following time limits:
(a) A claim must be filed within 2 years after the date the care or services were rendered (and in the case of continuous care, payment will not be made for any part of the care rendered more than 2 years prior to filing claim), or
(b) In the case of case or services rendered prior to a VA adjudication allowing service-connection:
(1) The claim must be filed within 2 years of the date the veteran was notified by VA of the allowance of the award of service-connection.
(2) VA payment may be made for care related to the service-connected disability received only within a 2-year period prior to the date the veteran filed the original or reopened claim which resulted in the award of service-connection but never prior to the effective date of the award of service-connection within that 2-year period.
(3) VA payment will never be made for any care received beyond this 2-year period whether service connected or not.