Why Won't My Address Verify / Validate?

Why won't my address validate

USPS Doesn't Recognize My Address!

For an address to be valid, it must match a corresponding address in the official USPS address database which can be accessed through the USPS APIs. If an address contains any incorrect data, it will not match a corresponding address in that database, and is therefore "invalid". Sometimes, an address will not validate because the address is marked as "vacant" by the USPS. Additionally, a new address, an unregistered address, or one located within a postal code primarily serviced by PO boxes, would all fail to validate. The best way to be sure an address is valid is to verify the address before you mail or ship something.

Table of Contents:

How to Perform Address Validation: A Detailed Guide

Some addresses won't verify because, for one cause or another, they're invalid.

It's a painful truth, and it happens to the best of us. You think you're being smart. You think you're taking all the right steps, and validating your addresses before you try to ship something. And then, the unthinkable happens: Your address is invalid.

But there are logical explanations for events like these, and we can all find peace by seeking to understand the "why" of our situation. In other words, if you want to know what to do or how to fix it, you have to know what broke first. And before you can do that, you need to know what it's supposed to look like when it does work.

Address Validation

Address validation (often called address verification) is the process of checking to see if an address is real. And it's a simple process; explaining it is as easy as 1-2-3:

  1. Address Standardization and Parsing
  2. Checking the Database
  3. Returning a Value

Let's look at how to use the Smarty address verification API to perform these steps.

Step 1: Address Standardization and Parsing

First, a submitted address is standardized. This means that any incorrect formatting is rectified. House number, street name, city, etc. are all organized, spelled, and abbreviated correctly, according to the official standards of the postal system that the address belongs to. In the US, for instance, "Street" is changed to "St.", "Utah" is changed to "UT," house numbers are listed before street names, and so forth. This is done so that the address can be properly matched against USPS address validation.

During this step, other minor errors are also corrected. Misspelled street or city names are fixed, and missing information is filled in. This can only go so far, however—there's little that standardizing can do if the given address lists the wrong street name, or if the street name is missing. City names are possible if the postal code and street address are correct. Likewise, a missing or incorrect street designation can be fixed, as long as there's not more than one street with that name in the city.

Here's an example of a correct address:

2116 Beresford Rd., Smallville, KS 67524 

Now suppose that the aforementioned address had been submitted with some incorrect information or an incorrect format. Standardizing can fix things like an incorrect street designation, misspelled city, or missing ZIP Code, provided it has enough other information for context:

2116 Beresford St., Smllvile, KS

(Wrong street designation, misspelled city)

It can't fix things like an incorrect street address or city name, or an incorrect city or state name if the postal code is missing:

2115 Hartford Rd., Smallville, KS 67524

(Incorrect address number, incorrect street name)

In short, if it can identify what it should be, then it can make the correction, but without the proper context clues the address is just wrong. Which leads us to the other half of step 1: parsing. Address parsing in general is an effort to disassemble a line of data, identify its distinct parts, and label them. This is a technique frequently applied to address validation, as it helps make both the standardizing and validating steps more effective.

Properly identifying the moving parts of an address can make it possible to fill in or correct more data that would normally be possible with standardization alone. This means there's a better chance of your address validating, even if you wrote some of it down wrong.

Like standardizing however, parsing is not foolproof; parsing often runs into little hiccups, like when trying to differentiate between

123 Bedford St., Martin, Colorado 


123 Bedford, St. Martin, Colorado 

where the first address lists "Bedford Street", and the second lists "Saint Martin city", with the problem words abbreviating to an identical "St."

Parsing is usually done in conjunction with standardizing, though a few validation providers do it as a final step after validation.

Step 2: Checking the Database

Once address cleansing has been performed and properly labeled via standardization and parsing, it's then taken and compared against a relevant database. The database used is the one that's the authoritative standard for whichever postal system you're using. Usually that database is the one kept by the postal organization run by that nation's government, like the USPS in the United States. A search is made to see if the address in question is on the official list, and if it is, it "validates", and is marked as a real, active address.

Failure to validate is the focus of this article, but the many different "whys" deserve their own explanations, so we'll circle back to it in a little bit. The short answer is that any address not listed in the database doesn't exist as far as the postal system is concerned, so it's marked "invalid."

In practice, sometimes you aren't validating an address in order to mail a letter or package. Instead, you just need to know that the address is real. This occurs frequently in the process of merging and managing customer databases. Since the USPS only includes addresses that they deliver to and since there are millions of addresses where the USPS doesn't offer door delivery, Smarty starts with the USPS address database and then adds additional public and private sources to give broader coverage. When an address validates that didn't originate from the USPS database, we will tell you so.

Taking this approach, allows you to validate addresses for shipping purposes but also for database management or anything in between.

Step 3: Returning a Value

Last, the address data is returned to the user, complete with a valid/invalid status. This is accompanied by, if the validator provides it, an explanation of why it didn't validate or what part of the address failed to validate.

The response a validation provider returns to you may also include any supplemental information that the provider compiles regarding addresses that are submitted to them. Many providers include things like geocodes that correspond to the address, RDI labels, or time zone information. This supplemental information can range from nonexistent to exhaustive, depending on the company providing it.

This concludes our tour of the address validation process.

Bad Addresses

Now for the fun part. Addresses go wrong and fail to validate for a number of reasons, so while this is not an exhaustive list, what we've put together here is thorough. The following list should cover just about every problem you're likely to experience.

Input Error

Never underestimate the power of humans messing up. Mistakes in the way the data is input, if not screened, often go unnoticed until much later. But even if you're keeping an eye out for them, you're still going to run into entries that are typed in incorrectly. Severe misspellings, flipping or scrambling numbers in the street address or the postal code—a little slip of the key like that can cause your address to be invalid.

Incorrect Information

Similar to the above reason, sometimes information is just inaccurate. A wrong street name is put in, or city name, or postal code. Basically, any inaccuracy too severe for standardization to correct will make the address invalid.

Missing Information

Sometimes the problem is not that information is wrong, sometimes the problem is that the information is missing. It's really hard to validate an address if you don't know the house number or street name. You'll be able to verify the accuracy of the city/state/postal code relationship, but without the actual location of the destination, you're up a creek.


On occasion, information is fake. People might falsify an address to hide an identity or steal one, or to sign up for duplicates of things (among other reasons). Whatever the case, the falsification of information can cause an address to come back with an "invalid" result (or worse, you might be accidentally validating someone else's address, without knowing it).

Not Serviced

Sometimes the postal service you're validating against doesn't service an area directly. Everything from PO box–only ZIP Codes in the US to war-torn areas in a third-world country, there are just some places where the postman doesn't make house calls. If the physical address is not receiving mail, it means that it won't be registered in the database, and that means any mail addressed to it will be sent back where it came from.

Not Registered

Regardless of which country or what postal service you're dealing with, an address needs to sign up with that postal service if it's to receive any mail. It's not the postal system's job to keep track of every available address that exists. It's their job to keep track of which addresses want mail. If you don't speak up, they assume you either don't want it or don't exist (see below). In either case, they won't be giving VIP status to an address that's not on the list.

New Address

Similar to unregistered addresses, a new address may not yet have had time to sign up for mail, or perhaps the mail system is still processing and adding them to the list. The postal service isn't keeping track every time a new house or building springs up out of the ground; that burdens on you. If you occupy a new structure, and you want to be receiving mail, it's your job to make sure the post office is aware of your presence. Failure to do so will result in an invalid address.


If no one is using the address, there's no one to sign the address up, so it's not on the list.

Does Not Exist

Every now and again, you're looking at an address that doesn't exist. Sometimes it's an address that's recently been condemned, demolished, or otherwise no longer in use. More often, it's because the address never existed in the first place. No one has a use for an imaginary address. The post office has no use for it, you have no use for it. So a validation of the address will just tell you that it can't find the address, making it invalid.

How Do I Get the USPS to Recognize My Address

Getting the United States Postal Service to recognize your address doesn't need to be difficult but it may take a few months to take effect. So, the sooner you get started the better. Addresses managed by the United States Address Management System (AMS) allows the public to submit address changes. You can find your local AMS office by entering your city and state or ZIP Code here.

Get the USPS to recognize my address step

You will then be provided with the address and phone number of your local AMS office who is in charge of your address. They will be able to aid you in getting your address added or corrected with their system.

Get the USPS to recognize my address step two

"But UPS Delivered There; That Means It's Valid, Right?"

You may be aware that private carriers like UPS, FedEx, and DHL will deliver to locations not recognized as valid in the authoritative databases maintained by organizations like USPS. If so, you're probably wondering what that means. Do they have their own database, and is it more accurate? Is there something wrong with the authoritative database? How do the private carriers get away with shipping to these aberrant addresses?

Private carriers market themselves on their willingness to go places that the primary carrier won't. Often, they'll even carry objects and substances that carriers like USPS won't touch. But that doesn't mean they're better, or that the addresses they deliver to are "valid" in the truest sense. Here's a few examples:

  • Physical location delivery for addresses serviced by PO boxes—because private carriers don't have any control over PO boxes, they can't deliver there. Instead, they make home deliveries, bringing the mail or package to the physical location as if that had been the mailing address all along. Since it's remote places where this tends to be a problem, and home delivery is required, your shipping costs will likely be higher to accommodate for the extra work they'll have to do.

  • Delivery to locations that don't/can't receive mail—places like warehouses that don't have a place for normally delivering things like letters and small packages. Under these conditions, it's usually larger objects that are shipped, and the private carrier is serving a function similar to a cargo shipping company. Because these are special locations, and because larger objects often require larger delivery vehicles and special tools for use in delivery, it can cost extra.

  • Addresses not registered/outside the service area—private carriers are also willing to go just about anywhere there's someone to receive mail. From the doomsday planner that wants to live off the grid, to the Inupik tribe on a remote island in Alaska, private carriers boldly go where no mailman has gone before. But that kind of trailblazing means going out of the way and, you guessed it, that makes it cost more.

You might think it's great that a private carrier can go to all these magical and exotic places. But by definition, if they're delivering to places that aren't valid, that means you can only ship via private carriers (who, you know, cost more).

Now it bears mentioning that courier services like UPS and FedEx sometimes have their own address validation tools, but you should know that at least in their case, not all validation is created equal. These tools don't validate in the truest sense, they just tell you whether they would be willing to take your package to the location to see if it's real. And we have to tell you, shipping a package is a terrible way to validate an address.

For example, the UPS validating tool only covers the 50 US states, and it excludes military and diplomatic post office destinations. Those are valid addresses that are serviced by the USPS on a regular basis, and UPS can't tell you that they're real.

Likewise, the FedEx tool lacks some of the accuracy of more reliable validation, like the USPS address validation tools that we provide. For instance, it uses AVS to help fill in missing data, since it doesn't standardize. As for the actual validation, rather than comparing the address against an authorized list, The FedEx system just checks to see if the given address matches a real state, city, and street, then checks the house number to see if it falls within the available ranges on that street. If it does, it "validates" to FedEx standards.

That means FedEx is potentially validating the address to imaginary homes and businesses, and that you might not know your shipment isn't going to be delivered until you get a box in the mail with a "Return to Sender" sticker on it. They probably don't mind, since they get paid either way, but we're betting that you do.

Here's where the discrepancy comes from, using the US as an example: private carriers are not maintaining a separate postal system. They are using a system that is already in place—a system established and maintained by their competitor, USPS. They're not aggregating and keeping their own database of addresses. All they're doing is delivering things.

This is why we use authoritative databases when we validate. Though private carriers can reach locations that the databases say don't exist, they can't be counted on to tell you when an address is real and few, if any, offer international validation (and we can just imagine the fun of an international package being returned to sender). What is international address validation ?

What Do I Do When an Address is Invalid?

For some causes of invalid addresses, there's nothing you can do. For starters, if someone falsified address information, then there is little you can do to track down the correct information. But if the problem was that someone mashed the keys when typing it in, or there was a common mistake in names of places, a human touch can often resolve what a computer finds impossible. So here are a few ideas on coping with bad addresses.

Double check your data: perhaps there's something you've missed. Maybe a mistake was made at some point during entry, or something didn't copy properly. It never hurts to give it a second look.

Look for common errors: reversed numbers, commonly misspelled words, checking for accurate street designations, you know, the little things. The kinds of things that you might not think much of, but that the postmen and women need clarification on, if they're going to get the mail to the right place. As humans, we're creatures of habit, and among our habits are habitual errors. So give the address a look-over, and check for the things you get wrong again and again.

Is your address really a PO box?: It may be a real address, but if that house or business is part of a "post office box only" postal area, you're not going to get a solid validation on it. So check and see if you're testing an address that won't be registered with the postal system due to the local service structure.

For US addresses, there are a number of tools that can do this for you. In fact, we can do it, and it won't cost you a dime. Just plug in the city, state, and 9 digit ZIP Code into our address verification demo and we'll give you a quick breakdown of the ZIP Code, including its "type." If the type is "S" (for "standard") then your address is just invalid. But if the type is "P" (for "PO box"), then you need to know the box number if you ever intend to get mail to those recipients.

Something else you should know: if you do know the PO box number (or think you know it), you can validate it, just like you would a physical address. It means the same thing: it's a real address, and it's currently being used. Here, we can show you how to send mail to a PO box

Fill in missing data: Missing data can be a real problem when you're trying to validate, so make sure you've filled in everything you can. The more information you can give, the more accurate the validation will be. If you're given an invalid response, double-check and make sure that you've supplied as much of the address as possible, and give it another go.


"Invalid-ness" is a real problem. If it hasn't affected you yet, it has likely affected someone you know. Every day addresses are coming up invalid, and if left untreated, packages and letters will be returned to sender by USPS as an Insufficient Address or another type of error. As with many things, the road to healing begins with prevention: validation can help you identify problem addresses, and though not every invalid address can be cured, you can find peace of mind in the knowledge of which of your addresses are real.

So remember, an invalid address has a reason. Those reasons can be the key making a successful effort at address validation, if you know them. And knowing, after all, is half the battle.

Ready to get started?