--- title: "Area code 840: California, United States" url: "https://lookvalid.com/area-code/840.md" canonical_url: "https://lookvalid.com/area-code/840" last_updated: "2026-10-23" type: "reference" summary: "Area code 840 serves California, United States. Number formats, numbering rules, a live phone validator and the other codes in California." --- # Area code 840: California, United States Area code 840 serves California, United States. Number formats, numbering rules, a live phone validator and the other codes in California. NANPA lists 124 central office codes (prefixes) in use in area code 840, held by 14 holders across 19 rate centers. T-Mobile USA holds the most prefixes, 32 (26%). 100% of the prefixes are pooled, which means their thousands-blocks can belong to different companies. The FCC unwanted-call data has 97 complaints on file for 94 numbers in 840, most often filed as "Unwanted Calls". These are consumer reports, not findings. ## Facts - In service since: 2021-02-23 - Time zone: Pacific (P) - Assigned overlays: 909 (1992-11-14) - Prefixes in use: 124 - Pooled prefixes: 124 (100%) - Rate centers: 19 - Companies holding prefixes: 14 - Assignment dates on file: 2020-12-23 to 2026-08-11 (124 prefixes) - ZIP codes in its places: 31 ## Rate centers | Rate center | Prefixes | Share | | --- | --- | --- | | POMONA | 16 | 13% | | ARROWHEAD | 14 | 11% | | FONTANA | 12 | 10% | | S BERNDINO | 12 | 10% | | CHINO | 8 | 6% | | CLAREMONT | 8 | 6% | | ONTARIO | 7 | 6% | | UPLAND | 7 | 6% | | 11 other rate centers | 40 | 32% | ## Carriers | Holder | Prefixes | Share | | --- | --- | --- | | T-Mobile USA | 32 | 26% | | Fractel | 26 | 21% | | Onvoy | 21 | 17% | | New Cingular Wireless PCS | 16 | 13% | | Verizon Wireless | 12 | 10% | | Bandwidth.com CLEC | 4 | 3% | | 8 other carriers | 13 | 10% | A prefix holder is the company a code was assigned to, not necessarily a number's current carrier, because numbers can be ported to another company. ## History - 1992-11-14: Area code 909, named as the parent of 840 in the NANPA report, was in service. - 2021-02-23: Area code 840 went into service. ## Nearest area codes The area codes closest to 840, measured between the centers of the ZIP code places they serve, are 626 (about 21 miles), 657 (about 29 miles), 714 (about 29 miles), 951 (about 33 miles) and 562 (about 36 miles). ## ZIP codes 31 ZIP codes fall in places that have a rate center in this area code. The places with the most are Fontana, CA (5 ZIP codes), Ontario, CA (4 ZIP codes) and Pomona, CA (4 ZIP codes). A ZIP code and an area code are unrelated systems, so a ZIP code can sit in more than one area code and an area code spans many ZIP codes. ## Complaints on file 97 complaints for 94 numbers. Numbers whose latest complaint falls in each year: - 2023: 17 - 2024: 17 - 2025: 9 ## Questions ### Where is area code 840? NANPA assigns area code 840 to California, United States. ### In which state does area code 840 sit? California. 840 is one of 41 area codes the NANPA table assigns to the state. ### Which places does area code 840 cover? The places with the most ZIP codes among the rate centers in 840 are Fontana, CA, Ontario, CA and Pomona, CA. The rate center list on this page shows all of them. ### Who owns area code 840? NANPA assigns area codes. Within 840, T-Mobile USA holds the most prefixes, 32 prefixes or 26%. ### Which time zone does 840 use? The NANPA NPA report lists the time zone for 840 as Pacific (P). ### What year did 840 enter service? The NANPA NPA report gives an in-service date of 2021-02-23, so 840 has been in use since 2021. ### Does area code 840 have an overlay? Yes. 909 (in service 1992-11-14) shares the same area with 840, so numbers from all of them are local to each other. ### Which area codes are nearest to 840? The area codes closest to 840, measured between the centers of the ZIP code places they serve, are 626 (about 21 miles), 657 (about 29 miles), 714 (about 29 miles), 951 (about 33 miles) and 562 (about 36 miles). ### How many prefixes does area code 840 have? NANPA's report dated 2026-10-17 lists 124 prefixes in service in 840, spread over 19 rate centers and 14 holders. ### Are there complaints about 840 numbers? The FCC data on file has 97 complaints for 94 numbers in 840. They are unverified consumer reports. A number with no complaints on file is not proven safe. Sources: NANPA central office code report dated 2026-10-17; NANPA NPA report dated 2026-10-18; FCC unwanted-call complaints, data fetched 2026-10-17; ZIP code places from GeoNames (CC BY 4.0).