Area code 423: where it is and who calls from it
Area code 423 is in Tennessee.
Tennessee (two discontiguous portions of East Tennessee in the northeast and in the southeast)
| Where | Tennessee |
|---|---|
| Time zone | Eastern and Central Time ยท local time |
| In service since | 1995 |
| Overlay | Yes, with 729 |
| Prefixes assigned | 764 of 792 possible (96%) |
Overlay: 423 covers the same area as 729. Overlay areas use 10-digit dialing, so a seven-digit number alone won't connect, and neighbors can have different area codes.
Where 423 numbers started
Every prefix is assigned to a rate center, the local calling area it was set up in. These are the biggest in 423, with how many prefixes each has.
Plus 14 smaller rate centers.
Who holds 423 numbers
- Mobile carrier 33%
- Local phone company 28%
- Internet / business phone carrier 32%
- Paging service 1%
- Phone company 6%
| Carrier | Type | Prefixes | Share |
|---|---|---|---|
| AT&T (local phone) | Local phone company | 121 | 16% |
| CenturyLink / Lumen | Local phone company | 85 | 11% |
| AT&T Mobility | Mobile carrier | 80 | 10% |
| Verizon Wireless | Mobile carrier | 80 | 10% |
| T-Mobile (including Sprint) | Mobile carrier | 64 | 8% |
| Onvoy | Internet / business phone carrier | 58 | 8% |
| Level 3 (Lumen) | Internet / business phone carrier | 38 | 5% |
| Windstream (PAETEC) | Internet / business phone carrier | 33 | 4% |
| Bandwidth | Internet / business phone carrier | 30 | 4% |
| Comcast | Internet / business phone carrier | 17 | 2% |
Most prefixes are pooled: the 10,000 numbers in each are handed out in blocks of 1,000 to different carriers, and people can also take their numbers to another carrier. So the carrier shown is where the prefix started, not a guarantee about any one number.
States served: Tennessee.
Other area codes in Tennessee
Got a call from 423?
An area code tells you where a number was first assigned, not where the caller is. People keep their numbers when they move, and scammers can fake any number. If you weren't expecting the call, let it go to voicemail.
If the call shows a 423 number that matches the first six digits of your own, that's often neighbor spoofing. Use the box above to check the full number.
Area code facts from the NANPA area code database (updated 10/06/2026); prefixes and carriers from NANPA's central office code records (updated 2026-10-10). Place description adapted from Wikipedia, CC BY-SA 4.0.