Covered Entity means a health plan, health care clearinghouse, and health care provider who transmits any health information in electronic form in connection with a transaction covered by subchapter C. 45 CFR 160.102

CMS - Centers for Medicare & Medicaid Services

DHHS - U.S. Department of Health and Human Services

HCO - health care operations

Health Care Operations - 45 CFR 164.501

Health Care Provider - 45 CFR 160.103.

IIHI - Individually identifiable health information

Individually identifiable health information - 45 CFR 160.103

NPP - Notice of Privacy Practices

Notice of Privacy Practices - 45 CFR 164.520

OCR - Office of Civil Rights

PHI - Protected health information

Protected health information - 45 CFR 164.501

QPO - Qualified Protective Order

Qualified Protective Order - 45 CFR 164.512(e)

TPA - Third Party Administrator or Trading Partner Agreement

Third Party Administrator means an entity that processes health care claims and performs related business functions for a health plan.

Trading Partner Agreement - 45 CFR 160.103

TPO - treatment, payment, and operations (some times called health care operations)

For more information, see HIPAA glossary.