621491 — HMO Medical Centers
Description
This U.S. industry comprises establishments with physicians and other medical staff primarily engaged in providing a range of outpatient medical services to the health maintenance organization (HMO) subscribers with a focus generally on primary health care. These establishments are owned by the HMO. Included in this industry are HMO establishments that both provide health care services and underwrite health and medical insurance policies (as defined in the official U.S. Census Bureau 2022 NAICS Manual).
Exclusions & Cross-References
- Health practitioners or health practitioner groups contracting to provide their services to subscribers of pre-
- paid health plans are classified in Industry 62111, Offices of Physicians; Industry 621210, Offices of
- Dentists; and Industry Group 6213, Offices of Other Health Practitioners; and
- HMO establishments (except those providing health care services) primarily engaged in underwriting and
- administering health and medical insurance policies are classified in U.S. Industry 524114, Direct Health
- and Medical Insurance Carriers.
Overview Facts
Legacy SIC Concordance
Trace the historical mapping chain from the 1987 Standard Industrial Classification (SIC) to the modern 2022 NAICS code format.
- SIC 8011 - Offices and Clinics of Doctors of Medicine (via SIC1987:8011→NAICS1997:621491→2002:621491→2007:621491→2012:621491→2017:621491→2022:621491)
Suggested Product Service Codes (Advisory)
The following Product Service Codes (PSCs) are advisory suggestions aligned with this NAICS code. Note: NAICS and PSC codes map to different dimensions of procurement (industry vs. product/service). There is no official binding 1:1 crosswalk.
- PSC Q701 — Specialized Medical Support
Source: DoD DPCAP PSC Selection Tool (Ingested: 2026-06-29)
Frequently Asked Questions (FAQ)
Is NAICS code 621491 valid in 2022? ▾
Yes, 621491 is a valid 6-digit 2022 NAICS national industry code representing 'HMO Medical Centers' under Sector 62 in the official classification index.
What is the SBA size standard for NAICS code 621491? ▾
The Small Business Administration (SBA) has established a small business size standard of $44,500,000 for NAICS code 621491 (HMO Medical Centers), calculated based on receipts.
What is the legacy SIC equivalent for NAICS 621491? ▾
According to official Census Bureau concordance tables, NAICS code 621491 (HMO Medical Centers) maps to legacy 1987 Standard Industrial Classification (SIC) codes: 8011 - Offices and Clinics of Doctors of Medicine.
Related Pages & Tools
Further regulatory reference links for NAICS code 621491:
- Sector 62 Directory Hub — List of related industries in the Health Care and Social Assistance sector.
- SIC ↔ NAICS Crosswalk Tool — Look up mappings between legacy SIC codes and modern classifications.
- NAICS 621491 to SIC Crosswalk — Bidirectional mapping to legacy SIC codes (HMO Medical Centers).
- SBA Size Standards Guide — Complete rules and averaging periods for small business classifications.
- Calculating Annual Receipts Guide — Detailed worked example of revenue calculation rules.
- IRS Principal Business Activity Guide — How NAICS codes map to corporate and entity tax filings.