Home Health PDGM Billing: OASIS, NOA, and HIPPS Codes

Home health agencies operate under one of the most punishing payment models in Medicare. Under the Patient-Driven Groupings Model (PDGM), payment hinges on accurate OASIS responses captured within tight timeframes, on Notice of Admission filings made within 5 days of start of care, and on visit utilization staying above LUPA thresholds. A single missing data point in OASIS can drop a 30-day period from one case-mix group to another and cost hundreds of dollars. A late NOA can cost an entire month's payment. This guide walks through the components of PDGM billing and the operational habits that hold it together.

How PDGM works

PDGM replaced the prior 60-day episode payment system with 30-day periods grouped into 432 case-mix categories. Payment for each period is determined by five variables:

1. Admission source and timing. Whether the patient was admitted from a community setting or institutional setting, and whether the period is early (first 30 days) or late (subsequent 30-day periods).
2. Clinical group. One of 12 clinical groups based on the principal diagnosis (musculoskeletal rehabilitation, neuro/stroke rehabilitation, wounds, complex nursing interventions, behavioral health, MMTA-cardiac, MMTA-endocrine, MMTA-GI/GU, MMTA-infectious, MMTA-respiratory, MMTA-surgical, MMTA-other).
3. Functional impairment level. Low, medium, or high based on OASIS responses to specific functional items.
4. Comorbidity adjustment. No adjustment, low adjustment, or high adjustment based on secondary diagnosis combinations.
5. HIPPS code. The 5-character code that aggregates the above variables for billing.

The grouper software, fed by OASIS and the claim diagnosis codes, calculates the HIPPS code. Agencies that bill the wrong HIPPS see denials or recoupments. Agencies that capture OASIS inaccurately see persistently lower payments because the grouper outputs the wrong group.

OASIS accuracy is everything

The Outcome and Assessment Information Set (OASIS) is the standardized assessment instrument that drives PDGM payment, quality reporting, and Star Ratings. The current iteration (OASIS-E and successors) captures roughly 100 items including functional status, cognitive function, behavioral health, social determinants, and clinical conditions.

High-impact OASIS items for PDGM

• M1800 Grooming, M1810 Upper Body Dressing, M1820 Lower Body Dressing: Drive functional impairment level.
• M1830 Bathing, M1840 Toilet Transferring: Drive functional impairment level.
• M1860 Ambulation/Locomotion: Drive functional impairment level.
• M1033 Risk for Hospitalization: Quality measure with star rating impact.
• M2020 Management of Oral Medications: Functional and quality impact.
• M1021 Primary Diagnosis: Drives clinical group selection.
• M1023 Secondary Diagnoses: Drive comorbidity adjustment.

Clinicians who capture OASIS perfunctorily, copy responses from prior assessments, or fail to ask the questions in person systematically undermine agency revenue. OASIS accuracy is a clinical training issue first and a billing issue second.

The Notice of Admission (NOA)

Effective 2022, CMS replaced the Request for Anticipated Payment (RAP) with the Notice of Admission. The NOA is a one-time filing per beneficiary admission, submitted within 5 calendar days of start of care.

Late NOA penalties

Each day past the 5th calendar day reduces the 30-day period payment by 1/30. If an NOA is submitted on day 8, the agency loses 3/30 (10%) of the period payment. NOA filed on day 35? The agency loses the entire first 30-day period payment. The clock is unforgiving and does not stop for weekends or holidays.

NOA workflow essentials

1. SOC tracking: A daily report identifying every new SOC that needs an NOA filed.
2. OASIS lock and review before NOA submission to ensure principal diagnosis aligns with clinical group expectations.
3. Same-day filing protocol when feasible, particularly for Friday SOCs.
4. NOA acceptance verification: Confirm the MAC accepted the NOA before treating it as submitted.

HIPPS codes and the grouper

The Health Insurance Prospective Payment System (HIPPS) code is a 5-character alphanumeric code that summarizes the case-mix group for billing. Under PDGM, the HIPPS structure encodes:

• Position 1: Admission source and timing combination.
• Position 2: Clinical group.
• Position 3: Functional impairment level.
• Position 4: Comorbidity adjustment.
• Position 5: Reserved or quality indicator.

Agencies should not calculate HIPPS manually. The grouper software, supplied by CMS or the EHR vendor, calculates HIPPS from OASIS and claim data. The agency's job is to ensure inputs are accurate and that the HIPPS on the claim matches the grouper's output. Mismatches trigger denials or post-payment audits. CMS HHA grouper documentation details current versions.

LUPA thresholds: don't underutilize

The Low Utilization Payment Adjustment (LUPA) applies when the visit count in a 30-day period falls below a case-mix-specific threshold. Below the threshold, Medicare pays per-visit rates instead of the full PDGM payment, often a 50-70% revenue cut for that period.

LUPA thresholds vary by case-mix group, ranging from 2 to 6 visits. Agencies should:

• Track each period's visit count daily, not at month-end.
• Identify periods at risk of LUPA early in the period.
• Coordinate clinical and scheduling teams to ensure plan-of-care visits are delivered.
• Document any LUPA that does occur (patient refusal, hospitalization) to support audit defense.

Note: Visits should never be added solely to avoid LUPA. Visits must be medically necessary and clinically appropriate. The integrity issue is reaching threshold through legitimate care, not gaming utilization.

Face-to-face encounter compliance

The Affordable Care Act requires that the certifying physician (or allowed non-physician practitioner) personally see the patient face-to-face within 90 days before or 30 days after the home health start of care. The encounter must be documented and the documentation must:

• State the date of the encounter.
• Confirm the encounter is related to the primary reason for home health.
• Be signed and dated by the certifying provider.
• Be retained in the home health record (the agency cannot rely on the certifying provider's records alone).

Insufficient F2F documentation is among the most common causes of home health denial. Agencies should obtain and review F2F documentation before or shortly after start of care, not at billing time.

Common PDGM denial causes and remediation

The most frequent home health denials and what causes them:

• Late NOA: Front-end SOC tracking and 5-day filing protocol.
• Insufficient F2F documentation: Pre-SOC documentation review with certifying physicians.
• OASIS-claim diagnosis mismatch: OASIS scrubbing before lock; claim coding aligned with M1021/M1023.
• Plan of care signature delays: 30-day signature deadline; tracking and physician follow-up.
• Therapy reassessment timing: 30-day and 13/19 visit reassessment deadlines.
• Homebound status documentation: Each visit narrative must support homebound status.

The Bottom Line

Home health PDGM is unforgiving. Accurate OASIS, on-time NOA, defensible F2F documentation, and proactive LUPA management are not optional; they are the operational backbone of agency revenue. Agencies that build process discipline around these four areas collect at the top of the curve. Agencies that don't accumulate avoidable losses faster than they realize.

Related: Home Health Billing Services · SNF PDPM Billing · Denial Management