Do you buy or sell things on eBay? Many PCMech readers do.

Do you buy things from sites like NewEgg or TigerDirect? Many PCMech readers do.

As great as technology is, in the United States we all rely on the postal system to ship and receive all our physical items.

To ensure shipped stuff get to where it’s supposed to go, you should always use ZIP + 4.

In the United States, all postal addresses have a ZIP code. ZIP means Zone Improvement Plan and is properly written as ZIP and not Zip or zip.

A standard ZIP code is 5 digits long, such as 12345 (which incidentally is Schenectady, New York).

The "+4" is a four-digit extension to the five-digit ZIP for a total of nine. It is separated by a dash. And example is 12345-6789 (a postal code assigned to General Electric Company).

Why does ZIP + 4 matter?

Whether you are sending or receiving stuff via postal mail, ZIP + 4 will ensure that packages will get to their intended locations the first time, every time.

Put very simply, using ZIP + 4 can mean the difference between a package or letter getting there or not getting there, so you might as well give yourself the advantage by using +4’s.

How to find your ZIP + 4

Go here: http://zip4.usps.com/zip4/

Enter your mailing address and submit. Your result will show up and you’ll get your ZIP + 4. Use it, remember it.

Using a post office (a.k.a. "P.O.") box?

Your +4 will usually contain your box number.

For example, if the ZIP is 12345 and your box number is 33, your ZIP+4 would be 12345-0033. And yes, the zeroes must be present if your box number is under 4 digits long. 12345-33 doesn’t work.

You should verify your box address via the link above just to be on the safe side.

Live in an apartment complex?

Some apartment complexes (usually larger ones) have "ranges" of ZIP + 4’s. For examples, "buildings 1 thru 3" may have a particular ZIP + 4 while "buildings 4 thru 8" may have another.

When using the ZIP + 4 link above, be sure to enter in your apartment number.

Tip: If you have both a number and a letter, like apartment 2B, enter it as "2B" and not "2 B" (the space counts – leave it out).

Shipping to someone else in the USA?

Example: You post an item for auction on eBay, someone buys it and you’re provided with the shipping address.

You can use the same way you found your ZIP + 4 to find theirs – just use the link above, enter in the address, submit and get the result.

Did you get too many results and don’t know which to pick?

If it’s the case where you submitted your address and what comes back is a whole bunch of choices where you’re confused as to which is correct, you have a few options.

1. Call the post office. They should be able to get your info very quickly because after all, shipping is their business.

2. Look at one of your bills. Be it an electric bill, phone bill or what-have-you, it should contain your ZIP + 4. How they magically know this stuff I have no idea.

If it’s the case where someone else’s ZIP + 4 has too many returned choices (such as with an eBay auction), contact the buyer and request an update including the +4 info. The buyer will most likely be very happy to provide the information as it shows that you care.

Remember, it totally sucks when you order something and it doesn’t get to you because of a shipping error. Using ZIP + 4 decreases the chances of shipping errors occurring dramatically – no matter which carrier you use.