The Early Warning System (EWS) was devised by the USPS to prevent address records from miscoding due to a delay in postal data reaching the USPS address matching files. The less recent the ZIP+4 File, the higher potential you have for miscoding addresses. When a valid address is miscoded because the address it matches to in the ZIP+4 File is inexact, it will result in what is termed a "broken address." Once an address is broken, the effect is permanent without manual intervention.
Using the EWS Auxiliary File with CODE-1 Plus will prevent "broken addresses" from occurring. EWS consists of records containing partial address information limited to the ZIP Code, street name, pre- and post-directionals, and a suffix. For an address record to be EWS-eligible, it must be an address not present on the most recent monthly production ZIP+4 File.