Address VerificationDirect Mail

ZIP+4 Codes – The Last 4 Digits of ZIP Code

By 2 September 2021September 4th, 2021No Comments

What are ZIP+4 Codes?

If you have ever tried sending direct mail to someone, you have likely come across the term ZIP+4 code (ZIP Plus 4 Codes). The origin of the ZIP code dates back as far as 1963. It was introduced as a solution to make mail travel faster. During its inception, the ZIP codes only consisted of 5 digits but, as the mail system grew bigger and more complex along with the growing population in the US, the 5-digit ZIP codes were no longer doing the job good enough. Hence in 1983, the USPS introduced the ZIP+4 codes, which are also known today as “+4 codes,” and the purpose of this ZIP+4 code is simply to add more precision to the standard five-digit ZIP codes.

verified address with zip code+4 codes

In a nine-digit full ZIP Code, the first five digits represent the specific delivery area or post office of an address, whereas the last four digits of the ZIP code indicate the delivery area down to a few blocks radius or specific delivery area. The entire nine-digit ZIP code, in effect, streamlines the delivery process for the USPS and ensures that your direct mail is sent or received with minimal delay. So it doesn’t matter whether you are sending mail or receiving one. It is important to know your ZIP+4 code so that the package can easily be delivered to its destination.

What are the Last 4 Digits of my ZIP code?

Many people are often unaware of their ZIP code’s last four digits, and their number is surprisingly high. Apart from this, most people are unaware of the full 9-digits ZIP code for the direct mails they send out. Although the post can be sent without the ZIP 4 code, it would be considered slow to move along and can take a while before it reaches the recipient. The ZIP code or Zone Improvement Plan was something the USPS came up with to make the postal service easy and quick across the country. The ZIP codes divide the country into different zones enabling the USPS to accelerate their postal sorting and delivery process effectively. Therefore, it is always best to provide the full 9-digits ZIP code if you want the letter or package delivered sooner rather than later.

The question now becomes how do I find the full ZIP code to the address I want to send a direct mail to. When it comes to businesses that send out regular direct mails to their customers, this question is even more crucial because they often work on deadlines. When working on a deadline, speed is vital, and the post reaches the customers even more urgently. Hence, businesses must turn to advanced address verification tools like PostGrid that can provide a complete address, including the full 9-digit ZIP codes for your address database. What makes it even better is that you are able to do this in a matter of seconds, and it only takes you a few clicks. There is no need for carrying out a ZIP 4 lookup for each and every address, all you need is a CSV file, and you can easily get the data you need with a few clicks.

Benefits of ZIP+4 Codes

When it was first launched, the five-digit ZIP code was a revolutionary step for the US postal service. It significantly simplified the way the USPS functioned and streamlined its operations. The ZIP 4 code was brought in later to accommodate the growing population. However, that’s not all the ZIP 4 code does. According to a recent study by the USPS, about 40 million Americans move every year, that is, 40 million address changes every year and potentially 40 million undelivered letters/packages every year. Although 40 million may not be the real number of undelivered mailings, it is safe to say that a large number of mailings may not be delivered or shipped to the wrong address if it wasn’t for the ZIP 4 code.As per the data from USPS, out of a whopping 158 billion mailed items in 2013, only a mere 4.3% of them were marked “Undeliverable as Addressed (UAA).” Had it not been for the ZIP 4 code, this number could have been a lot worse. The role of the ZIP 4 code doesn’t end there either. It further goes on to boost the delivery speed and accuracy of the USPS mailing significantly. This is evident from the one or two-day deliveries made by the USPS. 

But perhaps what can be considered the most significant benefit of the ZIP 4 code, especially for businesses, is that the ZIP+4 codes require address validation. In other words, in order to get the ZIP+4 code of an address, it must first be standardized and validated to exist. In Layman’s term, an address with a ZIP 4 code can be sure to exist and also deliverable. And the cherry on top for the businesses using the ZIP+4 code is that they can help with getting your business bulk mailing discounts.

How are ZIP Codes Used

The 9-digits full ZIP code works in parts. For example, consider a direct mail is sent to New York City from Dallas, the carrier that first receives your mail from Dallas need not know the exact delivery address of the recipient. The mail first needs to be forwarded to the appropriate mail carrier, which in this case is the state of New York. Now, here is where the ZIP code comes into the picture for the first time during the travel of your direct mail. As mentioned before, the ZIP codes are assigned to post offices all around the country by USPS, and each posy office has at least one ZIP code assigned to it. In case the post office handles postal services to more than one ZIP code, it will have more ZIP codes assigned to it.

The first five digits are used at this stage to ensure that the direct mail is sent to the correct post office. At this stage, there is no point bothering with the ZIP 4 code at this point. Once the direct mail reaches the destined post office, the first 5-digit of the ZIP code becomes practically irrelevant other than cross-checking the address. Once the direct mails are received at the relevant post office, the ZIP 4 codes can then be used to figure out where the mail is delivered. The ZIP 4 code allows assigning the right person for the delivery based on their delivery route, thereby streamlining the entire delivery process.

USPS Five-Digit ZIP Codes

Now that we have an overview of the two parts of the 9-digits ZIP, we can now discuss how exactly the ZIP code helps identify your most accurate location. The best place to start this is the USPS five-digit ZIP codes that we are all familiar with. Like we discussed before, they are most commonly used to indicate the post office that will take it to its final destination. However, most of us don’t know that each number in the five-digit ZIP code is significant to its destination. The first digit of your five-digit ZIP code signifies the national area, while the next two digits signify the sectional center or large city post office. The last two digits of the five-digit ZIP code give the associate post office or delivery area, thereby giving the people at USPS a comprehensive idea of the postage destination.

Furthermore, the ZIP codes allow the postal worker to effectively deliver as many postages as he/she can in a day. In essence, you may treat the five-digit ZIP code as the post office’s address, and although some post offices deal with posts with more than one ZIP code, normally, each post office has just one ZIP code. Do not imagine the ZIP codes as “boundaries,” but rather think of them as delivery routes that are not constrained by any geographic or administrative boundaries. They may cross city, state, or even country lines. In a way, you may even say that they are governed by where the delivery truck goes.

It should come as no surprise to you that there are certain special ones even among ZIP codes. “Military” ZIP codes are one of the special ZIP codes, and they can be used for everything from military bases, domestic or otherwise, to battleships. These are unique codes and serve a specific purpose of being individualistic from the standard ones to avoid any form of confusion. It is also possible for businesses and organizations to get their own ZIP code due to the high volume of mail they receive every day. This is very practical for both the business and USPS. The business usually has an internal mail department that can presort mail before distributing it inside the company. Similarly, the direct mails sent out from the company are also presorted. Furthermore, these firms also enjoy the benefit of bulk mailing discounts thanks to their internal mail department.

ZIP+4 Codes – The Last 4 Digits of ZIP Code

If you want your direct mail delivered the fast and most accurate way possible, you’ll need to provide the ZIP+4 code and the normal five-digit ZIP. However, the ZIP 4 code is only available for the addresses that are standardized and validated to be real. The ZIP code’s last four digits indicate a very specific delivery route that includes the mail truck’s actual path taken for travel in a single drop-off. Typically this route consists of ten to twenty homes/locations. Sometimes the ZIP 4 codes are also given to PO boxes. They usually get their own ZIP 4 code that more often than not matches with the box number.

💡 Also Read: ZIP Code API

Since the ZIP+4 code digits are based on delivery routes rather than permanent boundaries, the last four digits of ZIP codes can often be subjected to change. Although the five-digit ZIP code also changes from time to time, their changes are far less frequent as compared to the ZIP+4 codes. In fact, it is unlikely that the five-digit ZIP code of a place will change while you are still living there as they remain the same for most of the time. On the other hand, the ZIP 4 code can change much more frequently and may sometimes change once a month based on a number of factors. These factors include the number of postal employees working, the route taken by the delivery truck, etc.

Full Zip Code Lookup

Businesses who want to optimize their direct mails, whether it be for a campaign or for sending out important documents like bills, need to include a full ZIP code on the posts they send. The full ZIP code of a mailing address ensures that your post reaches its destination fast and efficiently. The full mailing ZIP code of an address also offers much higher deliverability because these addresses are standardized and validated to be real. Therefore, the more accurate and efficient your address verification system, the better your direct mailing process will be for your business. The best way for you to carry out a full zip code lookup for business purposes would be to use advanced address verification tools such as PostGrid. With an bulk address verification, like PostGrid, you can easily upload your address database, small or big, as a CSV file and you can easily get the verified version of your address database. Not only does PostGrid verify the address for you against the official postal address database of USPS, but also it fills in missing data, including the full 9-digit zip code for every address. You can even use PostGrid’s Address lookup API for implementing an address autocomplete feature on your website that would let you type in their address and generate their full address. The autocomplete feature can come in handy for your other marketing efforts, such as landing pages, by providing a convenient way for the user to type in their details and, in effect, encourages conversions as they make the desired action (Filling the form in this case).You can take it a step further by fully automating your business’s direct mail process by using PostGrid’s fully-documented REST API to send out personalized letters, checks, or postcards to your target audience. You can either send the direct mails on-demand or at scale, depending on your requirements. With a deliverability rate of 99.99%, PostGrid’s print and mail API and platform automate, optimizes the entire process involved in direct mailing, saving you valuable time and effort, which can now be utilized for the more important aspects of your business.

Full ZIP Code Lookup for Offline Communication and Cross-Channel Campaigns

Once you have a full 9-digit ZIP code added to your database’s addresses, you can significantly improve your offline communication capabilities. You can further use this data for your cross-channel marketing campaigns. It is evident that the full zip code lookup can greatly help businesses and marketing domains in many ways. They also come with certain limitations. Before you can employ advanced automation tools for your business’s offline communication and cross-channel campaigns, you should consider its advantages and disadvantages.

Advantages of Full ZIP Code Lookup for Offline Communication

The shipping quality of the offline communication methods is greatly improved when you carry out a full ZIP code lookup and use the ZIP+4 code, and it ensures the offline communications are delivered in a single drop-off. Another advantage of a ZIP+4 code lookup is that the addresses are subjected to a standardization process. Then the standardized address is subjected to validation with the official postal address database of USPS. This makes sure the address is deliverable, reduces your return rates, and effectively improves the ROI (Return of investment). 

The USPS encourages using ZIP+4 codes for bulk mailings by offering discounts because the ZIP+4 codes give USPS valuable information that will help them sort through their mails more efficiently. As a result, the USPS only has to spend minimal resources to mail pieces to their destination. Offline business communication is thus made not only more time-efficient but also cost-effective. By doing this, companies can optimize their operational expense and further contribute to a higher ROI.

Another aspect of your offline communication affected by the utilization of full ZIP code lookup is the speed. Throughout this article, we have mentioned many times how the full nine-digit ZIP code enhances the speed of operation and speed of delivery of the post. The ZIP+4 code enables the USPS to direct mail much faster, which is ideal for businesses that want to send out important documents such as invoices, bills, or bank statements. The documents reach their destination in the shortest possible time and minimize the risk of late delivery, which effectively improves your customer service quality.

Disadvantages of Full ZIP Code Lookup for Offline Communication

Although the full ZIP code lookup tools significantly enrich the customer data and are invaluable in terms of efficiency, there is a risk of it integrating poorly with an automated mail printing and delivery system. Unless the solution of your choice is fully automated, like PostGrid, that allows you to carry out a full ZIP code lookup and have them printed and mailed to the right destinations, you may end up hiring a separate team to handle the offline communications. Such a measure could affect your budget and keep your staff away from doing the more important work than organizing mail fulfillments. Similarly, not having a fully automated system like PostGrid can become a nightmare if the offline mailings are managed poorly by the team that takes care of them. There will always be the scope of human error in your offline communication system.

Advantages of Full ZIP Code Lookup for Cross-Channel Marketing

Using an advanced address verification tool like PostGrid for a full ZIP code lookup allows you to get a more comprehensive and data-driven idea about the geographic area your target audience lives in. You can use this to collect additional demographic data of the target audience. Once you get your hands on this type of data, you can then utilize it to learn the average household income, median age, and other such nifty details through governmental bodies’ official statistics. This kind of data can be a treasure trove for a capable marketing team. They can use it to come up with personalized advertising for the target audience through numerous marketing channels.

The channel used for the purpose could be anything from billboards to regionally-relevant, personalized postcards. Once you are able to relate to a specific customer or even customer group to their daily route, the marketing team can select the ideal product to be advertised based on the new data obtained. In effect, a full ZIP code lookup can lead to enhancing the marketing campaigns and their overall quality despite which marketing channel you decide to use. Furthermore, the accuracy of your cross-channel marketing is greatly improved through a full ZIP code lookup. This can be better utilized by companies or businesses that do not have extensive data on their customers and are constrained by their marketing budget to invest in advanced methods for collecting more data on their leads or customers.

Disadvantages of Full ZIP Code Lookup for Cross-Channel Marketing

As far as cross-channel campaigns are concerned, their effectiveness is to a great extent dependent on automation. The effective implementation of cross-channel is not feasible unless automated to get you the best possible result. The full ZIP code lookup offered by the USPS is not equipped with the advanced capabilities that are needed for the marketing automation of medium to large size companies. The USPS services offered for a full ZIP code lookup are pretty rudimentary and with limited data enrichment capabilities. For a business, it is highly impractical to use legacy solutions provided by USPS for determining the extended ZIP code of addresses in your database. As a result, your cross-channel marketing campaign may suffer.

Therefore, you need two things to get the desired result from your cross-channel marketing efforts: a marketing automation software and an advanced tech solution. This is where an advanced, fully-automated print and mail API solution like PostGrid comes into the picture. As tools like PostGrid are advanced and can be integrated into your website using API, it allows for complete automation of your direct mail campaigns. PostGrid’s capability to integrate to your business website along with its superior analytics makes it a one-stop solution for streamlining your cross-channel marketing efforts.

💡 Also Read: What is a postal code?


As we’re near the conclusion of this article, we find ourselves facing the best way to implement an extended ZIP code lookup for businesses. It is evident that, at a time when the competition is now harder than ever, businesses need to have an edge through reliable methods like cross-channel marketing and even offline communication through posts. Unlike the use of ZIP+4 codes by individuals or even small-scale businesses, companies with a fairly large address database can not afford to stick with traditional solutions.

Traditional solutions like USPS extended ZIP code lookup are not the right match for businesses regardless of size. It is, therefore, necessary for businesses to adopt a more simplified, accurate, and well-organized solution. Even partial automation, including address verification, may not get you the results you hope for. By using advanced tools, like PostGrid, you can streamline the entire process of cross-channel marketing. It can also save you valuable resources, which you can use for the more important goal of growing your business.

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