Updates are received approx every two weeks. Upon receipt the names are run against our current depositor names and those having held accounts over the past 12 months.

If we are running only the updated 314, how would we know that a customer opening an account today was previously included on an earlier list?

314 Jan - JOE BLOW listed
Search of depositor names does not reveal JOE BLOW as a depositor
May - JOE BLOW opens an account
314 May - Joe Blow not included
? - Because the name doesn't appear on the most recent 314 Update it's okay to NOT report this match

Please review the original instructions you received for 314(a) processing. The comparison to your customer files is "one time" only; they explicitly ask you not to compare the names of those opening new accounts against prior lists.