Why 5-Digit ZIP Codes Don’t Work

When isn’t 78368 the ZIP code for Hubert, Texas? When it’s the ZIP code for Mathis, San Patricio, Argenta or Sweeny Switch, Texas.

Lookups for 5-digit ZIP codes are often inaccurate, because, like the example above, a single ZIP code can be assigned to multiple U.S. cities. Why? Despite the geographic assignment of most ZIP codes, they generally correspond to address groups or delivery routes; sometimes more than one city can rest within a single group or route.

If you ship products within the United States, the best way to guarantee delivery is to use the latest ZIP + 4®.  Since many consumers often don’t know, and therefore don’t supply this number, the only way to accurately assign a city to a ZIP code is to use an address validation system that looks at the input street address and 5-digit ZIP code simultaneously and queries the United States Postal Service’s ZIP+4® database for accurate city assignments at the street address level.

The added group of four numbers acts as an extra identifier to aid in efficient mail sorting and delivery, pinpointing not only the city, but its geographic segment within a five-digit delivery area, such as: a city block, a group of apartments, a P.O. box or an individual high-volume receiver of mail (like the IRS).

About 15% of U.S. mail, (or over 90 million pieces) is deemed undeliverable-as-addressed (UAA).  Incorrectly spelled or formatted city names can mean mail returns, delays or one-way trips to mail recovery centers (MRC). Collectively, these facilities were once referred to as the “dead letter office” because once mail reaches that point, it’s destroyed.

Another multiple-city  ZIP code is 62812. It has six Illinois cities assigned to it: Rend City, Benton, Barren, Eastern, Steel City and West City.

When doesn’t mail sent to 62812 end up in Rend City, Illinois? When it’s redirected to a mail recovery center; waiting alongside other “dead mail” to be destroyed.

► Lookup ZIP+4 and see how Address Validation solves the ZIP code problem.



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