Healthcare Data GlossaryProvider
UPIN: Definition and Healthcare Context
Full name: Unique Physician Identification Number
The Unique Physician Identification Number (UPIN) was a six-character alphanumeric Medicare identifier assigned to physicians beginning in 1984. UPINs were required on Medicare claims for referring and ordering physicians. CMS replaced UPINs with NPIs for all HIPAA-covered transactions on May 23, 2007. Although no longer used in active Medicare billing, UPINs appear in legacy Medicare claims data and historical research datasets, particularly for studies using data predating the NPI transition.
Last updated: 2026-05-31Reviewed by: Dr. Jennifer Montecillo, MD — Gullas College of Medicine, 2019. Non-practicing medical reviewer.
How it’s used
- CMS PECOS Medicare Provider Enrollment: historical PECOS records reference UPIN-to-NPI crosswalk mappings maintained by CMS during the transition period.
- CMS NPPES NPI Registry: CMS published UPIN-to-NPI crosswalk files when NPPES launched to support legacy system migration.
Frequently asked questions
- What is a UPIN?
- A UPIN (Unique Physician Identification Number) was a legacy Medicare identifier for physicians, replaced by the NPI in May 2007.
- Is UPIN still used?
- No. UPINs are no longer valid for Medicare billing. They are retired identifiers that appear only in historical claims data from before May 2007.
- What replaced UPIN?
- The NPI (National Provider Identifier) replaced the UPIN for all HIPAA-covered transactions as of May 23, 2007.