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Out of all the components of a mailing address, the ZIP Code is one of the most essential. Generally, a 5-digit ZIP Code represents a city/state combination, but there can be many ZIPs in each city. A ZIP+4 Code represents a very specific postal delivery area within a 5-digit ZIP Code, sometimes as small as 5-10 houses or a single floor in a high-rise building.
Incomplete ZIP Code data will lead to delivery delays, returned mail, and higher postage costs. Address verification will determine deliverability of an address and then add the correct ZIP+4 Code. Accurate ZIP Code data will help qualify for USPS discounts and speed up delivery of mail—sometimes by as much as one or two days.