Typically, any time a VA Regional Office (RO) responds to a veteran’s disability claim the decision can be subject to a CUE request. If a veteran has enough evidence to prove that a mistake was made in the case, they are eligible to file a CUE. There is also no time limit for filing a VA CUE request. Even if a decision was made decades ago, if it was never appealed the veteran could challenge it today without consequence. However, the effective date (the day benefits will be retroactively paid from if the request is successful) will be the day the appeal claim is made, not the date of the original decision as with other appeal tactics such as HLR or supplemental claims.