The certifying officer assumes ultimate responsibility under 31 U.S.C. § 3528 for the validity of the claim; however:

(a) The traveler must ensure all travel expenses are prudent and necessary and submit the expenses in the form of a proper claim;

(b) The authorizing/approving official shall review the completed claim to ensure that the claim is properly prepared in accordance with regulations and agency procedures prior to authorizing it for payment.

Note to § 301-71.203:

You should consider limiting the levels of approval to the lowest level of management.