831
Area code
Statusin service
Introduced1998-07-11
JurisdictionCA, US
Local dialing7D
Time zonePacific
Last verified2026-09-17
Utilization 55.8% of assignable prefixes assigned
As of 09/17/2026
0%442 of ~792 assignable NXX values (200–999 excl. N11)100%
Prefix-level assignment does not equal number-level exhaustion; thousands-block pooling extends capacity. First assignment on record 2001-03-09, most recent 2026-09-03.
Area codes serve rate-center geographies, not municipal boundaries. “CA” identifies the jurisdiction, not an exact city footprint.
Top assignees
Ranked by assigned prefixes · initial assignee ≠ current carrier| Rank | Assignee | Prefixes | Share |
|---|---|---|---|
| 01 | PACIFIC BELL | 126 | 28.5% |
| 02 | NEW CINGULAR WIRELESS PCS, LLC | 35 | 7.9% |
| 03 | ONVOY, LLC - CA | 31 | 7% |
| 04 | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CA | 30 | 6.8% |
| 05 | LEVEL 3 COMMUNICATIONS, LLC - CA | 26 | 5.9% |
| 06 | 25 | 5.7% | |
| 07 | IP HORIZON LLC | 14 | 3.2% |
| 08 | T-MOBILE USA, INC. | 13 | 2.9% |
| 09 | METROPCS, INC. | 13 | 2.9% |
| 10 | U.S. TELEPACIFIC CORP. DBA TPX COMMUNICATIONS | 11 | 2.5% |
Important: these are initial assignees from NANPA CO-code records — the carrier a prefix was originally assigned to. Because of number portability, the current serving carrier of any individual number may differ.
Change history
Recorded events for this NPA- 1998-07-11Area code 831 entered service (created from 408).
Planning letters & orders
Primary documents| Date | Document | Subject |
|---|---|---|
| 1997-08-13 | PL-080 ↗ | Changes in Test Numbers and Effective Dates for California NPA Splits |
| 1997-05-22 | PL-063 ↗ | NANP- Split of 408 (California) Numbering Plan Area (NPA) |