Area code 423

About area code 423

423 is one of 8 geographic area codes serving Tennessee; NANPA records its in-service date as September 11, 1995. It is an overlay: 423 and 729 cover the same territory, so neighbors on the same street can have different area codes. It is in the Eastern and Central time zone. The places with the most assigned exchanges include Chattanooga, Johnson City, Bristol, Cleveland, and Kingsport. By population, its largest named places are Chattanooga, Johnson City, Kingsport, Cleveland, and Morristown.

Where 423 numbers are local

423 holds 20% of the 3,797 central office codes assigned in Tennessee, the 2nd most of the state's 8 codes. 48 Census places could be matched to rate centers with 423 exchanges; the most populous are Chattanooga (191,000), Johnson City (73,635), Kingsport (57,109), and Cleveland (50,232). Each place page lists the exact prefixes and carriers for that town.

How calls are dialed in 423

According to NANPA's dialing-plan data, local calls within 423 are dialed as ten digits (area code plus number) and toll calls as 1 plus ten digits. Because local calls need the area code, business cards, signage and website copy should always show the full ten-digit number. NANPA's dialing-plan note for this code reads: "1+10 digit dialing permissible at service providers discretion"

Carriers with 423 numbers

55 carriers hold the 764 central office codes assigned in 423. Bellsouth Telecomm INC d/b/a South Central Bell Tel has the most, with 119 (16%). 563 of the codes (74%) are pooled, meaning the code holder shares blocks of 1,000 numbers with other carriers instead of using all 10,000 itself. The code holder is not necessarily the carrier serving a given number today, since numbers can be ported between providers.

Local calling areas in 423

NANPA assigns each central office code to a rate center, the local calling area that decides whether a call is local or toll. 423 has codes in 75 rate centers. Rate center names in the file are abbreviations; where one matches a Census place, the table links to that city's local-number page.

Number supply in 423

An area code has 800 possible central office codes that start with 2 through 9, a few of which are reserved (such as N11 service codes and 555). 764 are assigned in 423, 96% of 800. 113 were assigned in 2020 or later.

Getting a 423 number for your business

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Porting a number you already use in area code 423 is free, and business texting is available once the carrier registration (10DLC) is approved; the registration carries a one-time $49 fee. Which specific numbers are open in a given area code depends on carrier inventory at the time you sign up.

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