U.S. Customs and Border Protection (CBP) accounted for firearms but did not always maintain accurate records for firearm locations or quantities of ammunition, as required. During the physical inventory of firearms in storage at 12 sites, the Office of Inspector General (OIG) identified 126 firearms not located at the address indicated in CBP’s system of record. CBP also did not ensure ammunition control, accountability, and loss reporting complied with policy requirements for sensitive assets. These issues occurred because CBP did not emphasize controls over ammunition. As a result, CBP may not know whether ammunition has been lost, stolen, properly accounted for, or provided to officers for unofficial training and practice.