I think the item you are talking about is the NACHA ARC SEC code which goes into effect as a rule on 3/15. FYI, according to this you need to provide the check number from the ACH file on the customer's statement.
This project is mainly aimed at the large lockbox providers who process tens of thousands of checks a day. Many of the lockbox providers are integrating this into their software configs. They are doing some of the checking against the R/T database in addtion to the Thomson EPICWare Database.