OASIS · Section M
M0020 — Patient ID Number
Response options, how to score it, and the error that most often sends the record back. Cited to Ch. 1, Item M0020.
OASIS-E2 v1.00.0 · ingested 2026-04-26
How to score it
Record the unique patient identifier assigned by your agency. This is an internal identifier — it does not need to match any CMS-assigned number. Use a consistent format across your roster so the same patient resolves to the same ID across episodes.
The common error
Generating a new ID for a returning patient who already has an agency record. Episodes for the same patient should share a stable M0020 so historical outcomes link correctly.
Source: OASIS-E2 Guidance Manual — Ch. 1, Item M0020. Verified 2026-04-26.
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