Sentence:  Whenever the Secretary of the Treasury , or the Comptroller General of the United States , as the case may be , shall find that any person <WSD>is</WSD> entitled to any such payment , after such payment shall have been received by such person , it shall be an absolute bar to recovery by any other person against the United States , its officers , agents , or employees with respect to such payment . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)