Tennessee, United States
Eastern Time
1:23 AM
Area Code
423
State / Province
Tennessee
Country
United States
Time Zone
Eastern Time
Area code 423 covers 75 cities and communities across Tennessee, based on telephone company rate center data.
Use the E.164 format for clickable phone links (RFC 3966):
<a href="tel:+14235550100">+14235550100</a><a href="tel:+14235550199">+14235550199</a>Look up which exchange in Tennessee a specific 423 number is homed to, and whether its block is wireline or wireless. See what a reverse lookup can establish before relying on the answer.
762 active prefixes in this area code, assigned as 5,860 thousands-blocks — pooling splits one prefix across several carriers, so each block is listed separately with the rate centre it is homed to, its carrier of record, and the switch that serves it.
Showing blocks 1–100 of 5,860
| NPA-NXX | Block | Rate centre | Type | Carrier (OCN) | Switch | LATA | LIR | Dates |
|---|---|---|---|---|---|---|---|---|
| 423-200 | 0 | Morristown | Wireless | POWERTEL NASHVILLE LICENSES, INC. (7476) | KNVLTNMA96Z | 474 | — | — |
| 423-200 | 1 | Morristown | Wireless | POWERTEL NASHVILLE LICENSES, INC. (7476) | KNVLTNMA96Z | 474 | — | — |
| 423-200 | 2 | Morristown | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-200 | 3 | Morristown | Landline or VoIP | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - TN (7278) | KNOXVILLE | 474 | — | — |
| 423-200 | 4 | Morristown | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | KNVLTNMANMD | 474 | — | — |
| 423-200 | 5 | Morristown | Landline or VoIP | PAETEC ITEL, LLC (829J) | KNVLTNMAYAY | 474 | — | — |
| 423-200 | 6 | Morristown | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | KNVLTNJHGT0 | 474 | — | — |
| 423-200 | 7 | Morristown | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | KNVLTNJHGT0 | 474 | — | — |
| 423-200 | 8 | Morristown | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | KNVLTNJHGT0 | 474 | — | — |
| 423-200 | 9 | Morristown | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | KNVLTNJHGT0 | 474 | — | — |
| 423-200 | A | Morristown | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | KNVLTNMANMD | 474 | — | — |
| 423-201 | 0 | La Follette | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | KNVLTNJHGT0 | 474 | — | — |
| 423-201 | 1 | La Follette | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | KNVLTNJHGT0 | 474 | — | — |
| 423-201 | 2 | La Follette | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | KNVLTNIIAMD | 474 | — | — |
| 423-201 | 3 | La Follette | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | KNVLTNIIAMD | 474 | — | — |
| 423-201 | 4 | La Follette | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | KNVLTNMANMD | 474 | — | — |
| 423-201 | 5 | La Follette | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | KNVLTNIIAMD | 474 | — | — |
| 423-201 | 7 | La Follette | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | KNVLTNIIAMD | 474 | — | — |
| 423-201 | 8 | La Follette | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | KNVLTNIIAMD | 474 | — | — |
| 423-201 | 9 | La Follette | Landline or VoIP | COMCAST IP PHONE, LLC (318J) | KNVLTNMAYHX | 474 | — | — |
| 423-201 | A | La Follette | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | KNVLTNMANMD | 474 | — | — |
| 423-202 | 0 | Johnson City | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | JHCYTNXCXIY | 956 | — | — |
| 423-202 | 1 | Johnson City | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | JHCYTNXCXIY | 956 | — | — |
| 423-202 | 2 | Johnson City | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | JHCYTNXCXIY | 956 | — | — |
| 423-202 | 3 | Johnson City | Landline or VoIP | CHARTER IP ENABLED SERVICES, LLC (792K) | BUVLTNAX0MD | 956 | — | — |
| 423-202 | 4 | Johnson City | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | JHCYTNXCXIY | 956 | — | — |
| 423-202 | 5 | Johnson City | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | JHCYTNXCXIY | 956 | — | — |
| 423-202 | 6 | Johnson City | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | JHCYTNXCXIY | 956 | — | — |
| 423-202 | 7 | Johnson City | Landline or VoIP | CHARTER IP ENABLED SERVICES, LLC (792K) | BUVLTNAX0MD | 956 | — | — |
| 423-202 | 8 | Johnson City | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | JHCYTNXCXIY | 956 | — | — |
| 423-202 | 9 | Johnson City | Landline or VoIP | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - TN (7278) | JHCYTNXCX3X | 956 | — | — |
| 423-202 | A | Johnson City | Landline or VoIP | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - TN (7278) | JHCYTNXCX3X | 956 | — | — |
| 423-203 | 0 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-203 | 1 | Chattanooga | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - TN (124F) | CHTGTNNSXFY | 472 | — | — |
| 423-203 | 2 | Chattanooga | Landline or VoIP | ONVOY, LLC - TN (525E) | CHTGTNNSXKY | 472 | — | — |
| 423-203 | 3 | Chattanooga | Wireless | BOOST SUBSCRIBERCO L.L.C. (490J) | CHTGTN1212Z | 472 | — | — |
| 423-203 | 4 | Chattanooga | Wireless | BOOST SUBSCRIBERCO L.L.C. (490J) | CHTGTN1212Z | 472 | — | — |
| 423-203 | 5 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-203 | 6 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-203 | 7 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-203 | 8 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-203 | 9 | Chattanooga | Wireless | BOOST SUBSCRIBERCO L.L.C. (490J) | CHTGTN1212Z | 472 | — | — |
| 423-203 | A | Chattanooga | Wireless | BOOST SUBSCRIBERCO L.L.C. (490J) | CHTGTN1212Z | 472 | — | — |
| 423-205 | 0 | Etowah | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-205 | 1 | Etowah | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-205 | 2 | Etowah | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-205 | 3 | Etowah | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-205 | 4 | Etowah | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-205 | 5 | Etowah | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-205 | 6 | Etowah | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-205 | 7 | Etowah | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-205 | 8 | Etowah | Landline or VoIP | TELNYX LLC (073H) | KNVNTNEC0MD | 474 | — | — |
| 423-205 | 9 | Etowah | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-205 | A | Etowah | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
| 423-206 | 0 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-206 | 1 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-206 | 2 | Chattanooga | Landline or VoIP | ELECTRIC POWER BOARD OF CHATTANOOGA (4645) | CHATTANOOGA | 472 | — | — |
| 423-206 | 3 | Chattanooga | Landline or VoIP | ONVOY, LLC - TN (525E) | CHTGTNNSXKY | 472 | — | — |
| 423-206 | 4 | Chattanooga | Landline or VoIP | ELECTRIC POWER BOARD OF CHATTANOOGA (4645) | CHATTANOOGA | 472 | — | — |
| 423-206 | 5 | Chattanooga | Landline or VoIP | ELECTRIC POWER BOARD OF CHATTANOOGA (4645) | CHATTANOOGA | 472 | — | — |
| 423-206 | 6 | Chattanooga | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CHTGTNGZ4MD | 472 | — | — |
| 423-206 | 7 | Chattanooga | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CHTGTNGZ4MD | 472 | — | — |
| 423-206 | 8 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-206 | 9 | Chattanooga | Landline or VoIP | ELECTRIC POWER BOARD OF CHATTANOOGA (4645) | CHATTANOOGA | 472 | — | — |
| 423-206 | A | Chattanooga | Landline or VoIP | ELECTRIC POWER BOARD OF CHATTANOOGA (4645) | CHATTANOOGA | 472 | — | — |
| 423-207 | 0 | Midway (Washington) | Landline or VoIP | COMCAST IP PHONE, LLC (318J) | JHCYTNXCXHY | 956 | — | — |
| 423-207 | 1 | Midway (Washington) | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | JHCYTNXC9MD | 956 | — | — |
| 423-207 | 2 | Midway (Washington) | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - TN (124F) | JHCYTNXCXNX | 956 | — | — |
| 423-207 | 3 | Midway (Washington) | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - TN (124F) | JHCYTNXCXNX | 956 | — | — |
| 423-207 | 4 | Midway (Washington) | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | JHCYTNXC9MD | 956 | — | — |
| 423-207 | 5 | Midway (Washington) | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - TN (124F) | JHCYTNXCXNX | 956 | — | — |
| 423-207 | 6 | Midway (Washington) | Landline or VoIP | COMCAST IP PHONE, LLC (318J) | JHCYTNXCXHY | 956 | — | — |
| 423-207 | 7 | Midway (Washington) | Landline or VoIP | TELEPORT COMMUNICATIONS AMERICA, LLC - TN (114F) | JHCYTNXCXRX | 956 | — | — |
| 423-207 | 8 | Midway (Washington) | Landline or VoIP | PAETEC ITEL, LLC (829J) | JHCYTNXCYZZ | 956 | — | — |
| 423-207 | 9 | Midway (Washington) | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | JHCYTNXC9MD | 956 | — | — |
| 423-207 | A | Midway (Washington) | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | JHCYTNXC9MD | 956 | — | — |
| 423-208 | 0 | Chattanooga | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CHTGTNGZ4MD | 472 | — | — |
| 423-208 | 1 | Chattanooga | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CHTGTNGZ4MD | 472 | — | — |
| 423-208 | 2 | Chattanooga | Wireless | POWERTEL ATLANTA LICENSES, INC. (7473) | CHTGTNNSXCZ | 472 | — | — |
| 423-208 | 3 | Chattanooga | Wireless | POWERTEL ATLANTA LICENSES, INC. (7473) | CHTGTNNSXCZ | 472 | — | — |
| 423-208 | 4 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-208 | 5 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-208 | 6 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-208 | 7 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-208 | 8 | Chattanooga | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | CHTGTN12X5Y | 472 | — | — |
| 423-208 | 9 | Chattanooga | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | CHTGTNNSX8X | 472 | — | — |
| 423-208 | A | Chattanooga | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CHTGTNGZ4MD | 472 | — | — |
| 423-209 | 0 | Chattanooga | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - TN (124F) | CHTGTNNSXFY | 472 | — | — |
| 423-209 | 1 | Chattanooga | Landline | BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL (9419) | CHATTANOOGA NINTH ST | 472 | — | — |
| 423-209 | 2 | Chattanooga | Landline | BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL (9419) | CHATTANOOGA NINTH ST | 472 | — | — |
| 423-209 | 3 | Chattanooga | Landline | BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL (9419) | CHATTANOOGA NINTH ST | 472 | — | — |
| 423-209 | 4 | Chattanooga | Landline | BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL (9419) | CHATTANOOGA NINTH ST | 472 | — | — |
| 423-209 | 5 | Chattanooga | Landline | BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL (9419) | CHATTANOOGA NINTH ST | 472 | — | — |
| 423-209 | 6 | Chattanooga | Landline | BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL (9419) | CHATTANOOGA NINTH ST | 472 | — | — |
| 423-209 | 7 | Chattanooga | Landline | BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL (9419) | CHATTANOOGA NINTH ST | 472 | — | — |
| 423-209 | 8 | Chattanooga | Landline | BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL (9419) | CHATTANOOGA NINTH ST | 472 | — | — |
| 423-209 | 9 | Chattanooga | Landline | BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL (9419) | CHATTANOOGA NINTH ST | 472 | — | — |
| 423-209 | A | Chattanooga | Landline | BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL (9419) | CHATTANOOGA NINTH ST | 472 | — | — |
| 423-210 | 1 | Tellico Plains | Wireless | UNITED STATES CELLULAR - TN (6278) | KNVLTNMA31Z | 474 | — | — |
| 423-210 | 4 | Tellico Plains | Landline or VoIP | ONVOY, LLC - TN (525E) | KNVLTNMA49Z | 474 | — | — |
Block-level assignments from the North American Numbering Plan administrator, via localcallingguide.com.
Assigned Prefixes
762
Assignment Blocks
5,860
Rate Centers
75
Carriers of Record
60
| Type | Blocks | Share |
|---|---|---|
| Landline | 885 | 15% |
| Landline or VoIP | 2,520 | 43% |
| Wireless | 2,455 | 42% |
| Carrier | Blocks |
|---|---|
| CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN | 962 |
| NEW CINGULAR WIRELESS PCS, LLC - GA | 733 |
| ONVOY, LLC - TN | 729 |
| BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL | 510 |
| BANDWIDTH.COM CLEC, LLC - TN | 449 |
| UNITED TELEPHONE-SOUTHEAST-TN DBA CENTURYLINK - TN | 269 |
| POWERTEL ATLANTA LICENSES, INC. | 234 |
| LEVEL 3 COMMUNICATIONS, LLC - TN | 220 |
| SUNCOM DBA T-MOBILE USA | 171 |
| PAETEC ITEL, LLC | 160 |
| 50 other carriers | 1,423 |
Carrier of record for each block. Numbers ported to another carrier keep their original block assignment, so this is not a lookup of who serves a given number today.
| Rate Center | Prefixes | Blocks |
|---|---|---|
| Chattanooga | 183 | 1,347 |
| Johnson City | 67 | 511 |
| Bristol | 37 | 286 |
| Cleveland | 32 | 272 |
| Kingsport | 32 | 244 |
| Morristown | 28 | 231 |
| Athens | 22 | 227 |
| Greeneville | 20 | 146 |
| La Follette | 16 | 142 |
| Newport | 15 | 118 |
| Elizabethton | 13 | 107 |
| Midway (Sullivan) | 12 | 48 |
| Rogersville | 12 | 114 |
| Blountville | 10 | 76 |
| Benton | 9 | 78 |
| Bulls Gap | 9 | 75 |
| Charleston | 9 | 81 |
| Sweetwater | 9 | 91 |
| Dayton | 8 | 59 |
| Erwin | 8 | 69 |
| Madisonville | 8 | 65 |
| Soddy Daisy | 8 | 73 |
| Limestone | 7 | 64 |
| Oneida | 7 | 39 |
| Pikeville | 7 | 53 |
| Sneedville | 7 | 55 |
| South Pittsburg | 7 | 58 |
| Fall Branch | 6 | 36 |
| Mountain City | 6 | 50 |
| New Tazewell | 6 | 38 |
| Bluff City | 5 | 27 |
| Butler | 5 | 36 |
| Copper Basin | 5 | 31 |
| Cumberland Gap | 5 | 51 |
| Englewood | 5 | 51 |
| Etowah | 5 | 40 |
| Jellico | 5 | 32 |
| Midway (Washington) | 5 | 40 |
| Spring City | 5 | 36 |
| Church Hill | 4 | 32 |
| Decatur | 4 | 39 |
| Georgetown | 4 | 34 |
| Jasper | 4 | 32 |
| Jonesboro | 4 | 33 |
| Mosheim | 4 | 28 |
| Sullivan Gardens | 4 | 35 |
| Surgoinsville | 4 | 34 |
| Tellico Plains | 4 | 31 |
| Baileyton | 3 | 22 |
| Collegedale | 3 | 33 |
| Fork Ridge | 3 | 24 |
| Hampton | 3 | 22 |
| Huntsville | 3 | 28 |
| Ooltewah | 3 | 18 |
| Roan Mountain | 3 | 21 |
| Stoney Creek | 3 | 21 |
| Vonore | 3 | 16 |
| Whitwell | 3 | 30 |
| Apison | 2 | 20 |
| Ball Play | 2 | 14 |
| Clinchport | 2 | 3 |
| Coker Creek | 2 | 12 |
| College Station | 2 | 3 |
| Deer Lodge | 2 | 3 |
| Dunlap | 2 | 12 |
| Fall Creek Falls | 2 | 3 |
| Niota | 2 | 13 |
| Oakdale | 2 | 5 |
| Riceville | 2 | 15 |
| Robbins | 2 | 16 |
| Sunbright | 2 | 3 |
| Wartburg | 2 | 5 |
| Nine Mile | 1 | 1 |
| Petros | 1 | 1 |
| Shady Valley | 1 | 1 |
A rate center is the telephone exchange area a number is homed to. It sets local calling boundaries, and is not the caller's current location.
423 now shares its territory with 729. Because of this overlay, local calls in this region must be dialed with all ten digits.
Area code 423 is a North American Numbering Plan (NANP) telephone area code assigned to Tennessee, United States. It is one of 8 area codes serving Tennessee. As population and demand for phone numbers grew, the region was divided into multiple numbering plan areas to avoid exhausting the available 7-digit number pool.
Yes. 423 is an active North American Numbering Plan (NANP) area code, currently assigned to Tennessee, United States. It is safe to answer or dial calls using this area code.
Area code 423 covers 75 cities and communities in Tennessee, including Apison, Athens, Baileyton, Ball Play, Benton, and 70 more localities. This is based on telephone company rate center data — the geographic areas carriers use to determine local calling boundaries and to assign numbers when a business or individual requests a phone number in a specific city.
All numbers in the 423 area code observe Eastern Time (IANA timezone: America/New_York). Eastern Time is UTC−5 in winter (EST) and UTC−4 in summer (EDT). When placing a call to a 423 number from a different time zone, check the current local time above to avoid calling outside of business hours.
From within Tennessee, dial the 7-digit local number directly if calling within the same rate center, or dial 1 + 423 + 7-digit number for long-distance calls within North America. From outside the US or Canada, dial your country's international exit code followed by 1 423 XXX XXXX. The country code for both the United States and Canada in NANP is +1.
Format 423 numbers using E.164 notation as required by RFC 3966: prefix with +1 and omit dashes and parentheses (e.g., +14235550100). This format ensures tel: links work correctly on all mobile browsers and VoIP apps. See the tel: URI formatting guide for complete examples.