Area code
423
423 is a United States area code. Under the North American Numbering Plan it belongs to Tennessee, which has 8 area codes in total.
Validate a number in 423
Paste a full number and the tool checks it against the numbering plan. It returns the standard formats, the line type the plan assigns and the area code region.
Digits with or without punctuation work. Numbers outside the US are read with the +country code.
Area code 423 at a glance
NANPA lists 761 central office codes (prefixes) in use in area code 423, held by 55 holders across 75 rate centers.
| Fact | Value |
|---|---|
| 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 in area code 423
| 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% |
Who holds the prefixes in 423
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.
| 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. Find which carrier a number is on, or browse the prefix holders.
History of area code 423
- 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.
Area codes nearest to 423
Distance is measured between the centers of the ZIP code places each area code serves, so it is a rough guide.
- 865 about 6 mi
- 828 about 92 mi
- 821 about 120 mi
- 606 about 121 mi
- 864 about 126 mi
Overlay codes in the same area
- 729
ZIP codes in area code 423
64 ZIP codes fall in places that have a rate center in this area code.
| Place | ZIP codes |
|---|---|
| Kingsport, TN | 6 |
| Cleveland, TN | 5 |
| Morristown, TN | 4 |
A ZIP code and an area code are unrelated systems. A ZIP code can sit in more than one area code, and an area code spans many ZIP codes.
Complaints on file for 423 numbers
3,050 FCC complaints are on file for 2,511 numbers in 423, most often filed as "Unwanted Calls". These are unverified consumer reports.
| Year of latest complaint | Numbers |
|---|---|
| 2023 | 132 |
| 2024 | 218 |
| 2025 | 162 |
Other area codes in Tennessee
Tennessee is one state with 8 area codes in the NANPA table. 423 is one of them.
Next to 423 in the numbering table
These are the codes just before and after 423 when all are sorted by number. They are neighbours on the list, not necessarily on the map.
What the area code does and does not tell you
A number that starts with 423 was first assigned in Tennessee. That is a fact about where the number began, and it is a useful hint when you check a form entry, for example a billing address in Tennessee next to a 423 phone number.
It does not show where the person is today. A number stays with its owner after a move or a change of provider (number portability), and mobile numbers travel with the handset. The area code also cannot tell you whether the line is active, who the carrier is, or whether the number is mobile or fixed: the plan shares those ranges. Read more about the area code, the numbering plan and line type.
Check numbers in bulk with the API
| Product | Credits | Docs |
|---|---|---|
| Phone Numbering-Plan Validation | 1 credit per valid number | API docs |
| Phone Intelligence (carrier and line status) | 1 credit per check (invalid numbers outside the US and Canada are free) | Product page |
Questions about area code 423
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.
Area code assignments: North American Numbering Plan Administrator NPA report, file dated 10/17/2026, retrieved 2026-10-17. Source file. New codes are assigned several times a year. Prefixes, rate centers, holders, time zone, in-service date and overlays: NANPA central office code report dated 2026-10-17 and NPA report dated 2026-10-18. Complaints: FCC consumer complaints open data, fetched 2026-10-17. ZIP code places: Postal code places and coordinates: GeoNames (geonames.org), licensed CC BY 4.0.