Prefix 303-276 — Denver, CO

NANPA CO code assignment, current as of July 28, 2026.

The 303-276 prefix belongs to area code 303 and is anchored to the Denver rate center (CO). In NANP terms, the prefix — or NXX — determines the rate center a number is billed against.

Denver is part of the Denver-Aurora-Centennial, CO Metropolitan Statistical Area. For routing purposes it sits in LATA 656. Numbers here keep Mountain time.

The assigned code holder is ONVOY, LLC - CO, operating company number 026D, assigned August 19, 2021. This is a pooled prefix — expect numbers within it to be split across more than one carrier in 1,000-number blocks.

Caller ID showing 303-276 is not proof the call came from Denver: spoofing and porting both detach numbers from their origin. To verify a caller, hang up and dial the organization's published number, and report suspicious calls to the FTC.

Neighboring prefixes

FAQ

Where is 303-276 located?

The prefix is assigned to the Denver rate center in CO, area code 303. It is part of the Denver-Aurora-Centennial, CO Metropolitan Statistical Area.

Which company owns 303-276 numbers?

ONVOY, LLC - CO holds the code, but the prefix is pooled — individual thousands-blocks can be assigned to other carriers, and numbers may be ported to any provider.

Is a call from 303-276 safe to answer?

The prefix itself says nothing about the caller. Legitimate Denver businesses and spoofed robocalls can both display it. Never share personal data with an unverified inbound caller.