---
title: "Area code 423: Tennessee, United States"
url: "https://lookvalid.com/area-code/423.md"
canonical_url: "https://lookvalid.com/area-code/423"
last_updated: "2026-10-23"
type: "reference"
summary: "Area code 423 serves Tennessee, United States. Number formats, numbering rules, a live phone validator and the other codes in Tennessee."
---

# Area code 423: Tennessee, United States

Area code 423 serves Tennessee, United States. Number formats, numbering rules, a live phone validator and the other codes in Tennessee.

NANPA lists 761 central office codes (prefixes) in use in area code 423, held by 55 holders across 75 rate centers.
South Central Bell Tel holds the most prefixes, 119 (16%). 74% of the prefixes are pooled, which means their thousands-blocks can belong to different companies.
The FCC unwanted-call data has 3,050 complaints on file for 2,511 numbers in 423, most often filed as "Unwanted Calls". These are consumer reports, not findings.

## Facts

- In service since: 1995-09-11
- Time zone: EC
- Assigned overlays: 729 (2025-09-05)
- Prefixes in use: 761
- Pooled prefixes: 560 (74%)
- Rate centers: 75
- Companies holding prefixes: 55
- Assignment dates on file: 2001-01-09 to 2026-06-18 (342 prefixes)
- ZIP codes in its places: 64

## Rate centers

| Rate center | Prefixes | Share |
| --- | --- | --- |
| CHATTNOOGA | 183 | 24% |
| JOHNSON CY | 67 | 9% |
| BRISTOL | 36 | 5% |
| CLEVELAND | 32 | 4% |
| KINGSPORT | 32 | 4% |
| MORRISTOWN | 28 | 4% |
| ATHENS | 22 | 3% |
| GREENEVL | 20 | 3% |
| 67 other rate centers | 341 | 45% |

## Carriers

| Holder | Prefixes | Share |
| --- | --- | --- |
| South Central Bell Tel | 119 | 16% |
| Centurylink | 83 | 11% |
| Verizon Wireless | 79 | 10% |
| New Cingular Wireless PCS | 78 | 10% |
| Onvoy | 54 | 7% |
| Level 3 Communications | 38 | 5% |
| 49 other carriers | 310 | 41% |

A prefix holder is the company a code was assigned to, not necessarily a number's current carrier, because numbers can be ported to another company.

## History

- 1954-01-01: Area code 615, named as the parent of 423 in the NANPA report, was in service.
- 1995-09-11: Area code 423 went into service.
- 1999-11-01: Area code 865 went into service and names 423 as its parent.
- 2025-09-05: Area code 729 went into service as an overlay in the same area as 423.

## Nearest area codes

The area codes closest to 423, measured between the centers of the ZIP code places they serve, are 865 (about 6 miles), 828 (about 92 miles), 821 (about 120 miles), 606 (about 121 miles) and 864 (about 126 miles).

## ZIP codes

64 ZIP codes fall in places that have a rate center in this area code. The places with the most are Kingsport, TN (6 ZIP codes), Cleveland, TN (5 ZIP codes) and Morristown, TN (4 ZIP codes). A ZIP code and an area code are unrelated systems, so a ZIP code can sit in more than one area code and an area code spans many ZIP codes.

## Complaints on file

3,050 complaints for 2,511 numbers. Numbers whose latest complaint falls in each year:

- 2023: 132
- 2024: 218
- 2025: 162

## Questions

### Where is area code 423?

NANPA assigns area code 423 to Tennessee, United States.

### In which state does area code 423 sit?

Tennessee. 423 is one of 8 area codes the NANPA table assigns to the state.

### Which places does area code 423 cover?

The places with the most ZIP codes among the rate centers in 423 are Kingsport, TN, Cleveland, TN and Morristown, TN. The rate center list on this page shows all of them.

### Who owns area code 423?

NANPA assigns area codes. Within 423, South Central Bell Tel holds the most prefixes, 119 prefixes or 16%.

### Which time zone does 423 use?

The NANPA NPA report lists the time zone for 423 as EC.

### What year did 423 enter service?

The NANPA NPA report gives an in-service date of 1995-09-11, so 423 has been in use since 1995.

### Does area code 423 have an overlay?

Yes. 729 (in service 2025-09-05) shares the same area with 423, so numbers from all of them are local to each other.

### Which area codes are nearest to 423?

The area codes closest to 423, measured between the centers of the ZIP code places they serve, are 865 (about 6 miles), 828 (about 92 miles), 821 (about 120 miles), 606 (about 121 miles) and 864 (about 126 miles).

### How many prefixes does area code 423 have?

NANPA's report dated 2026-10-17 lists 761 prefixes in service in 423, spread over 75 rate centers and 55 holders.

### Are there complaints about 423 numbers?

The FCC data on file has 3,050 complaints for 2,511 numbers in 423. They are unverified consumer reports. A number with no complaints on file is not proven safe.

Sources: NANPA central office code report dated 2026-10-17; NANPA NPA report dated 2026-10-18; FCC unwanted-call complaints, data fetched 2026-10-17; ZIP code places from GeoNames (CC BY 4.0).