38 U.S.C. § 715

1. (a)An employee of the Department is performing official duty during the period with respect to which the employee is testifying in an official capacity in front of either chamber of Congress, a committee of either chamber of Congress, or a joint or select committee of Congress.
2. (b)The Secretary shall provide travel expenses, including per diem in lieu of subsistence, in accordance with applicable provisions under subchapter I of chapter 57 of title 5, to any employee of the Department of Veterans Affairs performing official duty described under subsection (a).