38 CFR 17.131: Payment of abandoned claims prohibited.

Any informal claim for the payment or reimbursement of medical expenses which is not followed by a formal claim, or any formal claim which is not followed by necessary supporting evidence, within 1 year from the date of the request for a formal claim or supporting evidence shall be deemed abandoned, and payment or reimbursement shall not be authorized on the basis of such abandoned claim or any future claim for the same expenses. For the purpose of this section, time limitations shall be computed from the date following the date of request for a formal claim or supporting evidence.