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What’s the ZIP Plus-Four for?

March 17th, 2017

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You may have noticed the extra appendage of numbers added to a ZIP code called the plus-four, ZIP + 4, or add-on code. What is it for? The USPS considers the five-digit ZIP plus those additional four digits to be the most complete kind of delivery code. Introduced in 1983, the plus-four is a helpful ally in the ongoing drive for even more efficient delivery and sorting.

What do the numbers mean? 

What is the breakdown of the plus-four and what do the numbers mean? The first two numbers of the plus-four identify the larger area known as the sector. The last two identify the segment. Segment and sector are actually terms that identify very specific geographical areas that pinpoint more than just a numbered house on a street. As explained at this USPS source, “the final four digits identify geographic units such as a side of a street between intersections, both sides of a street between intersections, a building, a floor or group of floors in a building, a firm within a building, a span of boxes on a rural route, or a group of Post Office boxes to which a single USPS employee makes delivery.” It can also identify an individual high-volume receiver of mail.

The plus-fours and Stamps.com

The good news is that the guesswork is gone when it comes to using Stamps.com. Our software can help the USPS expedite the sorting and routing of the mail, ensuring that your recipient is not waiting for too long for your shipment. The Stamps.com software will apply the plus-four automatically for you as part of the Address Matching System (AMS) cleansing process. After you enter an address in the delivery address box, and click on Print Sample or Print Postage, Stamps.com will first have your address checked against the AMS.

You can modify your AMS settings within the software. You can do this by going to File and then Preferences in the main menu on the top of the software. Then, click on the Address tab. Here you can move the AMS slider. Setting it to “High” will always add the plus-four to your delivery address. The levels of “Medium” and “Low” will generate alerts for you when the plus-four cannot be verified. The plus-four is important!

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