November 29, 2023

NANPA: Understanding Telephone Number Types, Status, and Reputation

NANPA: Understanding Telephone Number Types, Status, and Reputation

Phone number allocation and planning have existed for decades. It standardizes phone number structures and helps ensure calls reach their intended destinations. Currently, the North American Numbering Plan Administration (NANPA) establishes the standards used by Canada, the United States, and the Caribbean.

What Is NANPA?

NANPA is a number standardization plan used by most of North America (Mexico doesn’t participate). The plan grew out of standardization practices attempted by AT&T in the 1960s. It has evolved over the decades to accommodate changes in technology, such as mobile phones and internet-based telephony.

What Makes Up a NANPA Phone Number?

NANPA uses a three-part structure with a total of 10 digits that follow a (XXX) XXX-XXXX pattern.

In the basic phone number structure, the first part is a three-digit number called the Number Plan Area (NPA). It’s commonly thought of as an area code, although it doesn’t always designate a specific region.

The second, three-digit number is called the Central Office Code or prefix. The Central Office Code can indicate which area the number connects to, but that’s less common as more people rely on mobile devices.

The third, four-digit number is called the Line Number. The line number is assigned to a specific destination within the Central Office Code. While many numbers can share an NPA and Central Office Code, numbers with the same NPA and Central Office Code must have a unique Line Number for each destination.

Types of Phone Numbers

The types of phone numbers managed by NANPA have grown over the last few decades as technology creates diverse communication options.


Landline numbers are fixed numbers that connect to a phone via physical wires. If you have a wired phone in your home, it likely uses a landline number.

Mobile Numbers

Mobile numbers direct calls to mobile devices, such as cell phones and smartphones. Carriers assigned mobile numbers to their clients. In many cases, clients can keep their mobile numbers when they change carriers as long as they stay in the same area.

VoIP Numbers

Voice over Internet Protocol (VoIP) numbers are assigned to specific users, such as a person or business, instead of a location. VoIP uses broadband to connect callers to each other. Therefore, you can take your VoIP number anywhere and use it with various devices, including computers and smartphones. Today’s VoIP technology supports chat and text messaging options.

Toll-Free Numbers (TFNs)

Toll-free numbers have NPAs that begin with “8.” For example, Caller ID Reputation’s toll-free number is 888-619-9586. Callers don’t pay for dialing toll-free numbers. Instead, any charges get directed to the number’s owner.

Vanity Numbers

Vanity numbers are typically toll-free numbers chosen by an organization. Useful vanity numbers provide some benefit to the owner. For instance, it might include a business’s name or industry. It could also include a numeric pattern that’s easy to remember.

Shared Use Numbers

Shared Use Numbers are vanity numbers used by several businesses in different areas. For example, 800-FLOWERS redirects callers to florists within their cities.

NANPA Number Resources and Codes

NANPA number resources and codes give users access to specific services as defined below.

N11 Codes

N11 codes are stand-alone three-digit numbers designated for specific services. For example, 911 connects callers to local emergency services. Other N11 codes include:

  • 311 for non-emergency police services.
  • 411 for directory assistance.
  • 711 for Telecommunication Relay Services that assist people with hearing or speech disabilities.

You can find the full list of N11 codes on the NANPA website.

Vertical Service Codes

Vertical service codes give landline users access to services provided by carriers. VSCs use a *XX format. Popular VSCs include *71 for call forwarding and *69 for dialing the number that most recently called you. With rotary phones, “11” replaces the *.

900 Codes

900 codes use “900” as the NPA. Consumers typically use them to access premium services from providers. As such, the bill goes to the caller rather than who owns the number. The cost of calling a 900 number comes from the service provider, not NANPA.

456 Codes

456 NPA codes were used to correctly route international calls. The code was deemed no longer necessary in 2017 and returned to the general purpose code pool in 2022.

555 Codes

555 is a central office code that can connect to a local service. For example, dialing 555-1212 can connect callers to local directory assistance. Few regional phone companies take advantage of the code, though. It’s most commonly used in fictional situations, such as when phone numbers appear in movies.

Analyzing a Phone Number’s History

Since most phone numbers currently use 10 digits, there is a limited pool of options. Because of this, numbers get released and reassigned as needed. This means some of your phone numbers could have histories that influence their reputations.

Accessing a phone number’s history offers insight into its origin and authentication processes. Numbers fall into categories like:

  • Never allocated
  • Allocation but never assigned
  • Assigned and added to the Do Not Call (DNC) register
  • Assigned and currently in the RND (reassigned number database)
  • Currently assigned and never reassigned
  • Currently assigned and previously in the RND

* Numbers can fall into more than one category. For instance, a number might be both in the RND and DNC.

The Importance of a Phone Number’s Reputation

Since many phone numbers have histories, you can inherit their reputation, including any call labels that appear on caller ID screens. Phone numbers typically fall within one of four categories:

  • None (very rare)
  • Good
  • Neutral
  • Bad

Using a number with a negative reputation can make it challenging to reach customers, clients, and leads.

Identifying Phone Number Flags

Caller ID Reputation makes it easy for you to identify any negative labels and manage your number reputations. Device Cloud provides screenshots from real smartphones connected to major carriers, so you know precisely what people see when you call them. When you spot negative labels, call blocks, and similar issues, you can rely on Number Redress Remediation to remedy the problems for you quickly and efficiently.

Want to learn more about the benefits of Caller ID Reputation’s platform? Start your free trial today.