Alberta, Canada
Mountain Time
1:17 PM
Area Code
403
State / Province
Alberta
Country
Canada
Time Zone
Mountain Time
Area code 403 covers 142 cities and communities across Alberta, based on telephone company rate center data.
Use the E.164 format for clickable phone links (RFC 3966):
<a href="tel:+14035550100">+14035550100</a><a href="tel:+14035550199">+14035550199</a>Look up which exchange in Alberta a specific 403 number is homed to, and whether its block is wireline or wireless. See what a reverse lookup can establish before relying on the answer.
780 active prefixes in this area code, assigned as 780 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 780
| NPA-NXX | Block | Rate centre | Type | Carrier (OCN) | Switch | LATA | LIR | Dates |
|---|---|---|---|---|---|---|---|---|
| 403-200 | A | Calgary | Wireless | TELUS MOBILITY CELLULAR, INC. (8301) | CLGRAB124MD | 888 | 808401 | — |
| 403-201 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY SHAWNESSY | 888 | 808401 | — |
| 403-202 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY BOWNESS | 888 | 808401 | — |
| 403-203 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY OGDEN | 888 | 808401 | — |
| 403-204 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY FOREST LAWN | 888 | 808401 | — |
| 403-205 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-206 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-207 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY FOREST LAWN | 888 | 808401 | — |
| 403-208 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CROWCHILD | 888 | 808401 | — |
| 403-209 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MOUNT ROYAL | 888 | 808401 | — |
| 403-210 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CAPITOL HILL | 888 | 808401 | — |
| 403-212 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KINGSLAND | 888 | 808401 | — |
| 403-213 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-214 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY ELBOW PARK | 888 | 808401 | — |
| 403-215 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-216 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-217 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KILLARNEY | 888 | 808401 | — |
| 403-218 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-219 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY AIRWAYS | 888 | 808401 | — |
| 403-220 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CAPITOL HILL | 888 | 808401 | — |
| 403-221 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-222 | A | Wrentham | Landline | TELUS COMMUNICATIONS, INC. (8084) | WRENTHAM | 888 | 808407 | — |
| 403-223 | A | Taber | Landline | TELUS COMMUNICATIONS, INC. (8084) | TABER | 888 | 808407 | — |
| 403-224 | A | Bowden | Landline | TELUS COMMUNICATIONS, INC. (8084) | BOWDEN | 888 | 808412 | — |
| 403-225 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY BONAVISTA | 888 | 808401 | — |
| 403-226 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY COUNTRY HILLS | 888 | 808401 | — |
| 403-227 | A | Innisfail | Landline | TELUS COMMUNICATIONS, INC. (8084) | INNISFAIL | 888 | 808412 | — |
| 403-228 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MOUNT ROYAL | 888 | 808401 | — |
| 403-229 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MOUNT ROYAL | 888 | 808401 | — |
| 403-230 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CRESCENT HEIGHTS | 888 | 808401 | — |
| 403-231 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-232 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-233 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-234 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-235 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY FOREST LAWN | 888 | 808401 | — |
| 403-236 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY OGDEN | 888 | 808401 | — |
| 403-237 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-238 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY OAKRIDGE | 888 | 808401 | — |
| 403-239 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CROWCHILD | 888 | 808401 | — |
| 403-240 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KILLARNEY | 888 | 808401 | — |
| 403-241 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CROWCHILD | 888 | 808401 | — |
| 403-242 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KILLARNEY | 888 | 808401 | — |
| 403-243 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY ELBOW PARK | 888 | 808401 | — |
| 403-244 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MOUNT ROYAL | 888 | 808401 | — |
| 403-245 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MOUNT ROYAL | 888 | 808401 | — |
| 403-246 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KILLARNEY | 888 | 808401 | — |
| 403-247 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY BOWNESS | 888 | 808401 | — |
| 403-248 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY FOREST LAWN | 888 | 808401 | — |
| 403-249 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KILLARNEY | 888 | 808401 | — |
| 403-250 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY AIRWAYS | 888 | 808401 | — |
| 403-251 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY OAKRIDGE | 888 | 808401 | — |
| 403-252 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KINGSLAND | 888 | 808401 | — |
| 403-253 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KINGSLAND | 888 | 808401 | — |
| 403-254 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY SHAWNESSY | 888 | 808401 | — |
| 403-255 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KINGSLAND | 888 | 808401 | — |
| 403-256 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY SHAWNESSY | 888 | 808401 | — |
| 403-257 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MCKENZIE | 888 | 808401 | — |
| 403-258 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KINGSLAND | 888 | 808401 | — |
| 403-259 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY KINGSLAND | 888 | 808401 | — |
| 403-260 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-261 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-262 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-263 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-264 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-265 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-266 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-267 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-268 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-269 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-270 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY HILLHURST | 888 | 808401 | — |
| 403-271 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY BONAVISTA | 888 | 808401 | — |
| 403-272 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY FOREST LAWN | 888 | 808401 | — |
| 403-273 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY FOREST LAWN | 888 | 808401 | — |
| 403-274 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY HUNTINGTON HILLS | 888 | 808401 | — |
| 403-275 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY HUNTINGTON HILLS | 888 | 808401 | — |
| 403-276 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CRESCENT HEIGHTS | 888 | 808401 | — |
| 403-277 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CRESCENT HEIGHTS | 888 | 808401 | — |
| 403-278 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY BONAVISTA | 888 | 808401 | — |
| 403-279 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY OGDEN | 888 | 808401 | — |
| 403-280 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY TEMPLE | 888 | 808401 | — |
| 403-281 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY OAKRIDGE | 888 | 808401 | — |
| 403-282 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CAPITOL HILL | 888 | 808401 | — |
| 403-283 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY HILLHURST | 888 | 808401 | — |
| 403-284 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CAPITOL HILL | 888 | 808401 | — |
| 403-285 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY TEMPLE | 888 | 808401 | — |
| 403-286 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY BOWNESS | 888 | 808401 | — |
| 403-287 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY ELBOW PARK | 888 | 808401 | — |
| 403-288 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY BOWNESS | 888 | 808401 | — |
| 403-289 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY CAPITOL HILL | 888 | 808401 | — |
| 403-290 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-291 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY AIRWAYS | 888 | 808401 | — |
| 403-292 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-293 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY TEMPLE | 888 | 808401 | — |
| 403-294 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-295 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY HUNTINGTON HILLS | 888 | 808401 | — |
| 403-296 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-297 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-298 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-299 | A | Calgary | Landline | TELUS COMMUNICATIONS, INC. (8084) | CALGARY MAIN | 888 | 808401 | — |
| 403-300 | A | Calgary | Landline or VoIP | SHAW TELECOM INC. - BC (497E) | CLGRABAS0MD | 888 | 808401 | — |
Block-level assignments from the North American Numbering Plan administrator, via localcallingguide.com.
Assigned Prefixes
780
Assignment Blocks
780
Rate Centers
142
Carriers of Record
18
| Type | Blocks | Share |
|---|---|---|
| Landline | 400 | 51% |
| Landline or VoIP | 123 | 16% |
| Wireless | 257 | 33% |
| Carrier | Blocks |
|---|---|
| TELUS COMMUNICATIONS, INC. | 400 |
| TELUS MOBILITY CELLULAR, INC. | 95 |
| ROGERS COMMUNICATIONS CANADA INC. | 80 |
| BELL CELLULAR, INC. | 64 |
| SHAW TELECOM INC. - BC | 59 |
| BELL WEST, INC. - ON | 22 |
| FIDO SOLUTIONS INC. - QC | 21 |
| DISTRIBUTEL COMMUNICATIONS LIMITED | 9 |
| ALLSTREAM INC. | 8 |
| GT GROUP TELECOM SERVICES CORP. | 5 |
| 8 other carriers | 17 |
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 |
|---|---|---|
| Calgary | 370 | 370 |
| Red Deer | 40 | 40 |
| Lethbridge | 32 | 32 |
| Medicine Hat | 23 | 23 |
| Canmore | 11 | 11 |
| High River | 11 | 11 |
| Strathmore | 11 | 11 |
| Brooks | 10 | 10 |
| Banff | 9 | 9 |
| Crowsnest Pass | 9 | 9 |
| Olds | 9 | 9 |
| Rocky Mountain House | 9 | 9 |
| Airdrie | 8 | 8 |
| Drumheller | 8 | 8 |
| Pincher Creek | 8 | 8 |
| Cochrane | 7 | 7 |
| Okotoks | 7 | 7 |
| Stettler | 7 | 7 |
| Claresholm | 6 | 6 |
| Ponoka | 6 | 6 |
| Three Hills | 5 | 5 |
| Hanna | 4 | 4 |
| Milk River | 4 | 4 |
| Sundre | 4 | 4 |
| Vauxhall | 4 | 4 |
| Veteran | 4 | 4 |
| Vulcan | 4 | 4 |
| Bowden | 3 | 3 |
| Cardston | 3 | 3 |
| Coronation | 3 | 3 |
| Didsbury | 3 | 3 |
| Lacombe | 3 | 3 |
| Oyen | 3 | 3 |
| Sylvan Lake | 3 | 3 |
| Bentley | 2 | 2 |
| Blackfalds | 2 | 2 |
| Bow Island | 2 | 2 |
| Carstairs | 2 | 2 |
| Coaldale | 2 | 2 |
| Consort | 2 | 2 |
| Cowley | 2 | 2 |
| Crossfield | 2 | 2 |
| Exshaw | 2 | 2 |
| Fort MacLeod | 2 | 2 |
| Granum | 2 | 2 |
| Innisfail | 2 | 2 |
| Lake Louise | 2 | 2 |
| Langdon | 2 | 2 |
| Magrath | 2 | 2 |
| Penhold | 2 | 2 |
| Picture Butte | 2 | 2 |
| Ralston | 2 | 2 |
| Taber | 2 | 2 |
| Trochu | 2 | 2 |
| Warner | 2 | 2 |
| Acadia Valley | 1 | 1 |
| Acme | 1 | 1 |
| Alix | 1 | 1 |
| Altario | 1 | 1 |
| Arrowwood | 1 | 1 |
| Barons | 1 | 1 |
| Bassano | 1 | 1 |
| Beiseker | 1 | 1 |
| Big Valley | 1 | 1 |
| Bindloss | 1 | 1 |
| Blackie | 1 | 1 |
| Bragg Creek | 1 | 1 |
| Brocket | 1 | 1 |
| Burdett | 1 | 1 |
| Byemoor | 1 | 1 |
| Carbon | 1 | 1 |
| Carmangay | 1 | 1 |
| Caroline | 1 | 1 |
| Castor | 1 | 1 |
| Cayley | 1 | 1 |
| Cereal | 1 | 1 |
| Cessford | 1 | 1 |
| Champion | 1 | 1 |
| Clive | 1 | 1 |
| Coutts | 1 | 1 |
| Craigmyle | 1 | 1 |
| Cremona | 1 | 1 |
| Delburne | 1 | 1 |
| Delia | 1 | 1 |
| Donalda | 1 | 1 |
| Duchess | 1 | 1 |
| East Coulee | 1 | 1 |
| Eckville | 1 | 1 |
| Elkwater | 1 | 1 |
| Elnora | 1 | 1 |
| Empress | 1 | 1 |
| Enchant | 1 | 1 |
| Etzikom | 1 | 1 |
| Foremost | 1 | 1 |
| Gadsby | 1 | 1 |
| Gleichen | 1 | 1 |
| Glenwood | 1 | 1 |
| Grassy Lake | 1 | 1 |
| Halkirk | 1 | 1 |
| Hays | 1 | 1 |
| Hilda | 1 | 1 |
| Hussar | 1 | 1 |
| Iron Springs | 1 | 1 |
| Irricana | 1 | 1 |
| Irvine | 1 | 1 |
| Jenner | 1 | 1 |
| Kananaskis | 1 | 1 |
| Leslieville | 1 | 1 |
| Lomond | 1 | 1 |
| Longview | 1 | 1 |
| Manyberries | 1 | 1 |
| Milo | 1 | 1 |
| Mirror | 1 | 1 |
| Morley | 1 | 1 |
| Morrin | 1 | 1 |
| Nanton | 1 | 1 |
| New Dayton | 1 | 1 |
| Nobleford | 1 | 1 |
| Nordegg | 1 | 1 |
| Raymond | 1 | 1 |
| Rimbey | 1 | 1 |
| Rockyford | 1 | 1 |
| Rolling Hills | 1 | 1 |
| Rosebud | 1 | 1 |
| Rumsey | 1 | 1 |
| Saskatchewan River Crossing | 1 | 1 |
| Schuler | 1 | 1 |
| Seven Persons | 1 | 1 |
| Sibbald | 1 | 1 |
| Spruce View | 1 | 1 |
| Stand Off | 1 | 1 |
| Standard | 1 | 1 |
| Stavely | 1 | 1 |
| Stirling | 1 | 1 |
| Sunchild O'Chiese | 1 | 1 |
| Tilley | 1 | 1 |
| Torrington | 1 | 1 |
| Turner Valley | 1 | 1 |
| Walsh | 1 | 1 |
| Waterton Park | 1 | 1 |
| Wrentham | 1 | 1 |
| Youngstown | 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.
403 now shares its territory with 368. Because of this overlay, local calls in this region must be dialed with all ten digits.
Area code 403 is a North American Numbering Plan (NANP) telephone area code assigned to Alberta, Canada. It is one of 5 area codes serving Alberta. 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. 403 is an active North American Numbering Plan (NANP) area code, currently assigned to Alberta, Canada. It is safe to answer or dial calls using this area code.
Area code 403 covers 142 cities and communities in Alberta, including Acadia Valley, Acme, Airdrie, Alix, Altario, and 137 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 403 area code observe Mountain Time (IANA timezone: America/Denver). Mountain Time is UTC−7 in winter (MST) and UTC−6 in summer (MDT). When placing a call to a 403 number from a different time zone, check the current local time above to avoid calling outside of business hours.
From within Alberta, dial the 7-digit local number directly if calling within the same rate center, or dial 1 + 403 + 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 1 403 XXX XXXX. The country code for both the United States and Canada in NANP is +1.
Format 403 numbers using E.164 notation as required by RFC 3966: prefix with +1 and omit dashes and parentheses (e.g., +14035550100). This format ensures tel: links work correctly on all mobile browsers and VoIP apps. See the tel: URI formatting guide for complete examples.