The USPS creates 10-20 new ZIP Codes each year, and it takes up to 5 years for people to fully utilize new ZIP Codes. Individual ZIP+4 Codes may change up to once a month since plus 4s tie to how many employees a post office has, changing coverage areas, new construction, etc. ...
the address is checked against the AMS data file to ensure that it exists as an active delivery point.[170] The USPS provides DPV on their website as part of the ZIP Code Lookup tool; there are also companies that offer services to perform DPV in bulk. ...