Tennessee · Central Time
423 Area Code
Area code 423 is in Tennessee, serving eastern Tennessee outside Knoxville, including Chattanooga and the Tri-Cities. It is in the Central Time zone (part of its territory observes Eastern Time). It shares its territory with overlay code 729, so 10-digit dialing is required.
Last updated October 1, 2026 · Source: NANPA
Where is the 423 area code?
423 is a Tennessee area code covering eastern Tennessee outside Knoxville, including Chattanooga and the Tri-Cities. In the wider directory it sits in the South region.
Cities in the 423 area code
- Chattanooga
- Johnson City
- Kingsport
- Cleveland
- Bristol
- Morristown
- Greeneville
- Elizabethton
- East Ridge
- Athens
- Red Bank
- Dayton
- Collegedale
- Rogersville
Counties served by 423
Hamilton County, Sullivan County, Washington County, Bradley County, Hamblen County, Greene County, Carter County, McMinn County, Hawkins County and Rhea County.
Time zone note: Eastern in Knoxville and Chattanooga; Central in Nashville, Memphis and most of the state.
423 overlay codes and dialing
The 423 territory is covered by an overlay of 2 area codes: 423, 729. All of them serve the same geographic area, and the original code is 423. Because more than one code covers the same ground, 10-digit dialing is mandatory — you must dial the area code for every local call. New phone lines may be assigned any of these codes.
History of the 423 area code
423 went into service on September 11, 1995, created when it was split from 615. It serves Chattanooga and the surrounding part of Tennessee, and today shares its territory with overlay code 729. For how codes are created, split, and overlaid, see how area codes work.
Is 423 a scam or spam risk?
423 is a legitimate geographic area code, not a premium or toll line, so a call from it costs you nothing extra. That said, scammers frequently spoof real local area codes to look familiar on caller ID. A genuine 423 number on your screen is no guarantee the caller is in Chattanooga, TN or trustworthy. See spam & scam-risk area codes for how spoofing works and how to respond.
Other Tennessee area codes
Explore more
See every code in Tennessee, compare codes across the South region, or view all Central Time codes. You can also browse the 4XX block or the complete numeric list of US area codes.
New to how this all works? Start with how area codes work, then read up on overlays, 10-digit dialing, and spam & scam-risk codes. To check another number, use the area code lookup tool.
Quick answers
423 area code FAQ
Where is the 423 area code?
The 423 area code is in Tennessee, covering eastern Tennessee outside Knoxville, including Chattanooga and the Tri-Cities, in the South region.
What cities are in the 423 area code?
Cities in the 423 area code include Chattanooga, Johnson City, Kingsport, Cleveland, Bristol, Morristown, Greeneville, Elizabethton, East Ridge and Athens.
What time zone is 423 in?
423 is in the Central Time zone. Eastern in Knoxville and Chattanooga; Central in Nashville, Memphis and most of the state.
What is the overlay for the 423 area code?
423 shares its territory with 729. Both codes (423, 729) serve the same area, so 10-digit dialing is required for every call.
When did the 423 area code start?
423 went into service on September 11, 1995.
Do I have to dial 10 digits for 423?
Yes. Because 423 is an overlay area, you must dial the full 10-digit number (area code + 7 digits) for every call.
Is 423 a toll-free or premium code?
No. 423 is a standard geographic area code, so calling it costs the same as any local or long-distance call on your plan. Toll-free calls use 800, 888, 877, 866, 855, 844 or 833.