Sentence:  Whenever the <WSD>Secretary</WSD> of the Treasury , or the Comptroller General of the United States , as the case may be , shall find that any person is 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:  the person who holds the secretaryship of the Treasury Department