An OFAC search is required for all vehicle transactions whether they are "cash" or "financed" deals. At the stores that I represent, the search is completed via the credit report. It will detail if there is a match found. There are several other companies out there that will also perform OFAC searches.
We have a written policy on OFAC searches, which includes instructions on how to determine if an OFAC match is a true match, and what to do if it is.
So far we have only had one true match. The FBI was in the dealership within 10 minutes.
Additional information can be found at
http://www.fincen.gov Hope this helps!