What is a Special Agency Check (SAC) ?
Generally it is the FBI criminal check done based on a fingerprint submission but I’m sure it can vary from agency to agency.
A SAC (Special Agreement Check) is where an individual’s fingerprints are electronically submitted to OPM by an agency to run a criminal history check. It can be done as a stand-alone check for the purpose of continuous evaluation, a follow-up to a report of arrest, used for the issuance of a government credential or in most cases, is the precursor to the submission of a full background investigation.