The 423 area code covers Chattanooga, Johnson City and 61 more places in Tennessee.
Area code 423 is in Tennessee, on Eastern Time and Central Time. In the 423 area, phone numbers are given out most in Hamilton County, then Sullivan and Washington counties. It has been in service since September 11, 1995. 729 covers the same area, so two neighbours can have different area codes.
- Where
- 8 counties in Tennessee, mostly Hamilton County, Sullivan County and Washington County
- Time zone
- Eastern Time and Central Time
- In service since
- September 11, 1995
- Shares its area with
- 729 (since 2025)
- Prefixes in use
- 764
- How to dial
- Local calls need all 10 digits: 423-555-0142.
Find out who called you from a 423 number.
Enter the full 10-digit number to see who it is listed to and the city and state on the listing. It is the same free check as our who called me lookup. To see only the caller ID name on the number, use our free CNAM lookup. To see whether it is a mobile, a landline or a VoIP line, use our free VoIP checker. To see which carrier a (423) number is on today, use our free carrier lookup.
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Chattanooga holds 24% of the phone prefixes in area code 423.
A prefix is the three digits after the area code, and NANPA assigns each one to a town. Counting the 764 prefixes in use shows where 423 numbers are actually given out.
- Chattanooga183 prefixes, 24%
- Johnson City67 prefixes, 9%
- Bristol38 prefixes, 5%
- Cleveland33 prefixes, 4%
- Kingsport32 prefixes, 4%
- Morristown28 prefixes, 4%
- Athens22 prefixes, 3%
- Greeneville20 prefixes, 3%
Also served: Midway, La Follette, Newport and Elizabethton and 51 smaller places.
BellSouth (AT&T) holds the most phone number prefixes in area code 423: 119 of 764.
NANPA, which runs the North American numbering plan, assigns each prefix (the three digits after the area code) to one carrier. Here is how the 764 prefixes in use in 423 divide between carriers; holders this page does not name are grouped as other carriers.
| Carrier | Prefixes | Share |
|---|---|---|
| BellSouth (AT&T)AT&T's landline company | 119 | 16% |
| CenturyLinkLandline company | 85 | 11% |
| AT&T MobilityMobile network | 80 | 10% |
| T-MobileMobile network | 64 | 8% |
| Level 3 (Lumen)Lumen's business and wholesale network | 38 | 5% |
| PAETEC (Windstream)Windstream's business phone network | 33 | 4% |
| 42 other carriers | 345 | 45% |
74% of these prefixes are pooled, which means the blocks of 1,000 numbers inside them can belong to other carriers. Any number can also have been moved to another carrier since, so this shows who holds the prefixes, not who serves a given number.
Want the carrier of one exact number? Our free carrier lookup checks it, because numbers move between carriers.
Source: NANPA central office code assignments, October 1, 2026.
423 has been split once and overlaid once since 1995.
1995
423 starts on September 11, 1995, split off from 615.
1999
On November 1, 1999, 865 splits off and takes part of the 423 area.
2025
On September 5, 2025, 729 is added on top of 423, so new numbers here can get either code.
A 423 number on your screen can still be a scam, because caller ID is easy to fake.
- Let an unknown call go to voicemail. A real caller leaves a message; a robocaller usually does not.
- Look the number up with the box above before you call back, because calling back tells a robocaller your line is live.
- Hang up on anyone who wants gift cards, crypto or a wire transfer, or asks you to read out a code that was just texted to you.
- Report unwanted robocalls at reportfraud.ftc.gov, or paste a suspicious message into our free scam checker.
The area codes closest to 423 are 865, 828 and 606.
This list measures the distance between the centres of each area, across state lines, and shows codes that share one area together.
Tennessee has 7 other area codes.
These are the questions people ask most about area code 423.
Where is area code 423?
423 covers Chattanooga, Johnson City, Bristol and Cleveland and 59 more places in Tennessee. In the 423 area, phone numbers are given out most in Hamilton County, then Sullivan and Washington counties.
What state is area code 423 in?
Tennessee. 423 is a Tennessee area code on Eastern Time and Central Time.
What cities use area code 423?
The places holding the most 423 prefixes are Chattanooga, Johnson City, Bristol, Cleveland, Kingsport, Morristown, Athens and Greeneville, out of 63 places in all. The count comes from NANPA's prefix assignments as of October 1, 2026.
Which phone company owns area code 423?
No single phone company owns 423. NANPA's records show BellSouth (AT&T) holds the most 423 prefixes, 119 of 764, followed by CenturyLink and AT&T Mobility. Numbers move between carriers, so check one exact number with a carrier lookup.
What time zone is area code 423 in?
423 is on Eastern Time and Central Time.
When did area code 423 start?
423 went into service on September 11, 1995, when it was split off from 615.
Is 423 the same area as 729?
Yes. 729 (since 2025) covers the same ground as 423. Nobody's number changed when it was added; new lines simply get whichever code has numbers left, so two neighbours can have different codes.
How do I dial a 423 number?
Local calls need all 10 digits: 423-555-0142.
Is 423 a toll-free number?
No. 423 is a regular area code for Chattanooga and Johnson City in Tennessee, not a toll-free one. The toll-free codes in North America are 800, 833, 844, 855, 866, 877 and 888.
What area codes are near 423?
The closest are 865 (Knoxville, Tennessee), 828 (Asheville, North Carolina), 606 (Corbin, Kentucky) and 864/821 (Greenville, South Carolina), measured between the centres of each area.
Who called me from a 423 number?
Enter the full 10-digit number in the lookup above. It returns the listed owner where there is a public record, where the number is registered, and whether it is a mobile, a landline or a VoIP line.
Is area code 423 a scam?
423 is a real Tennessee area code, so the code itself is not a warning sign. Scam callers fake local-looking numbers on purpose, so judge the call by what the caller asks for, and look the number up before calling back.
Put this lookup on your site: our free area code widget takes two lines of code and shows any US area code's state, time zone and local time.
Source: NANPA, the North American Numbering Plan Administrator: its area code database and prefix assignments, as of October 1, 2026.