TPUC: 423 Area Code Mandatory 10-Digit Dialing by August 2025

• Mandatory 10-digit dialing for all local calls within the 423 area code began on August 5, 2025.
• This change is due to an area code overlay, introducing the new 729 area code to the same geographic region.
• The Tennessee Public Utility Commission (TPUC) approved the overlay to ensure the availability of new telephone numbers.
• Affected areas include Chattanooga, Bristol, Johnson City, and Kingsport in Eastern Tennessee.
• Failing to dial 10 digits after the effective date results in uncompleted calls and a recorded instruction to redial.

Businesses operating within the 423 area code must update their communication systems, automated dialers, and internal protocols to accommodate mandatory 10-digit dialing by August 5, 2025, to avoid service disruptions and ensure continued client and stakeholder accessibility.

Residents and businesses operating within the 423 area code in Eastern Tennessee must prepare for a significant change in how they make local calls. Effective August 5, 2025, all local calls originating from or destined for the 423 area code will require 10-digit dialing, meaning callers must include the area code before the seven-digit telephone number. This new procedure applies universally, even for calls within the same area code.

This shift is a direct consequence of an area code overlay, which introduces the new 729 area code to the same geographic region currently served by the 423 area code. The overlay is designed to ensure a sufficient supply of new telephone numbers for the growing demand. While existing 423 numbers will not change, any new telephone lines or services activated on or after September 5, 2025, may be assigned numbers with the new 729 area code. These new 729 numbers will also necessitate 10-digit dialing from their inception.

The Tennessee Public Utility Commission (TPUC) formally approved these 423 area code dialing changes, implementing the overlay to address the impending exhaustion of available telephone numbers. An area code overlay allows for the introduction of a new area code within an existing geographic region without requiring current subscribers to change their primary area code. However, the trade-off is the mandatory adoption of 10-digit dialing for all local calls within that region.

The affected area encompasses two distinct, non-contiguous regions across Eastern Tennessee. Key communities impacted by this Eastern Tennessee 10-digit dialing requirement include Chattanooga, Bristol, Johnson City, and Kingsport, alongside numerous smaller towns and communities. The new 729 area code will serve this identical geographic footprint, ensuring continuity of service while expanding numbering capacity.

The transition to mandatory 10-digit dialing will affect anyone with a telephone number in the 423 area code. After August 5, 2025, attempts to dial a local number using only seven digits will result in an uncompleted call, followed by a recorded message instructing the caller to hang up and redial with the full 10-digit number. This change underscores the critical need for individuals and, particularly, businesses and organizations to update their communication systems.

Businesses operating within the 423 area code must update their communication systems, automated dialers, and internal protocols to accommodate mandatory 10-digit dialing by August 5, 2025, to avoid service disruptions and ensure continued client and stakeholder accessibility. This includes reprogramming PBX systems, alarm systems, speed dialers, and any other equipment that automatically dials telephone numbers. For any specific questions or concerns regarding this transition, individuals are advised to contact their respective telephone service providers.

Businesses and organizations operating within the 423 area code must update their communication systems, automated dialers, and internal protocols to accommodate mandatory 10-digit dialing by August 5, 2025, to avoid service disruptions and ensure continued client and stakeholder accessibility.

Source: Original reporting via {source}