HIPPS code 1GA31

A HIPPS code is the five-character string on a home health claim that encodes how Medicare classified a 30-day period. It is not an identifier — every character carries meaning, and together they explain exactly why a period paid what it paid. Paste one in and this decoder separates it back out into the four decisions behind it, plus the placeholder character. Change any decision and the code and its LUPA threshold change with it; both directions run the same CMS table, so they cannot disagree.

Character 1 — admission source and timing

Four possibilities, combining where the patient came from with whether this is the first 30-day period or a later one. Institutional means a qualifying inpatient stay — acute hospital, inpatient rehab, long-term care hospital, skilled nursing facility or inpatient psychiatric facility — in the 14 days before the period started. For a later period where the patient stayed on service, only an acute hospital stay counts. Everything else is community.

Character 2 — clinical group

One of twelve groups, A through L, set by the primary diagnosis on the claim. This is the character most often traced back to a coding decision made weeks earlier.

Character 3 — functional impairment level

Low, medium or high, scored from the OASIS function items and the hospitalization risk item (M1033). This is the character clinicians most directly influence, because it comes from how function was documented at assessment.

Character 4 — comorbidity adjustment

None, low or high, based on secondary diagnoses. Comorbidities that qualify for the high adjustment must appear in specific combinations, which is why a patient who is clearly complex can still score none.

Character 5 — placeholder

Always the same value. It carries no case-mix meaning and exists to keep the code five characters long.

How many payment groups are there in total?

Four admission-source and timing combinations, twelve clinical groups, three functional impairment levels and three comorbidity adjustments give 432 case-mix groups.

The HIPPS code is not what I expected. Where did it go wrong?

Work backwards through the characters. A surprising clinical group points at the primary diagnosis. A lower functional level than the patient warrants points at how function was scored on the OASIS. A comorbidity adjustment of none usually means the secondary diagnoses did not fall into a qualifying combination rather than that the patient has no comorbidities.

Can a HIPPS code change after the claim is submitted?

Yes. If the assessment or the diagnoses are corrected, the period regroups and the HIPPS code changes with it. That is why a correction to an OASIS can move payment even when nothing about the care delivered has changed.

Which year is this decoder built on?

The structure was verified against Table 13 of the CY 2026 HH PPS Final Rule (CMS-1828-F). The five-character structure has been stable since PDGM began, but case-mix weights are recalibrated annually, so the meaning of the characters outlasts the amounts they produce.