I recommend doing a full check of your customer base each time the OFAC list changes (but especially when names are added to the OFAC list). Otherwise, you might have a customer that opened an account 6 months ago and everything was fine, but today you might be required to freeze their account and report it to OFAC. If you're only checking annually, you could be at significant risk.
Jim Bedsole, CRCM, CBA, CFSA, CAFP
My posts - my opinions