Comparison · 2026

OASIS-E1 vs OASIS-E2: A Side-by-Side Comparison

A clear, structured comparison of OASIS-E1 and OASIS-E2 — what stayed the same, what changed, when each took effect, and what your agency needs to do to transition without payment leakage.

Quick Reference Comparison

Dimension OASIS-E1 OASIS-E2
Effective Date January 1, 2025 2026 (per CMS)
Replaces OASIS-E (Jan 2023) OASIS-E1
Structural Framework 5 time points · M-items · GG-items Same (preserved)
Section GG (Functional) IMPACT Act-aligned, refined from OASIS-E Further refinements; continued cross-setting alignment
Cognitive / Behavioral BIMS, PHQ-2/9, behavior items Updated administration guidance; same instruments
SDOH Items Housing, food, transportation, health literacy Expanded; refined item definitions
PDGM Mapping Clinical group + functional + comorbidity Same framework; potential payment-pattern shifts
HH QRP Submission iQIES; required time points Same submission requirements
EMR Vendor Updates Pushed automatically by HCHB, WellSky, etc. Same — pushed automatically by EMR vendors

What Stayed the Same

OASIS-E2 is an iterative update, so the foundational architecture is preserved:

  • Five required time points: SOC, ROC, Recertification, Transfer, Discharge
  • M-item structure across clinical, functional, and service utilization domains
  • Section GG functional assessment framework
  • PDGM payment mapping logic
  • Home Health Quality Reporting Program (HH QRP) submission requirements via iQIES
  • Star Ratings methodology
  • Conditions of Participation (CoP) compliance requirements

This means existing OASIS-E1 clinician workflows, EMR forms, and QA processes can be updated incrementally rather than rebuilt from scratch.

What Changed in OASIS-E2

  1. Section GG refinements. Updated item definitions, scoring guidance, and continued IMPACT Act harmonization with SNF (MDS), IRF (IRF-PAI), and LTCH (LTCH CARE) functional items.
  2. Cognitive and behavioral item updates. Refinements to BIMS administration, PHQ depression screening, and behavior frequency/impact items.
  3. Expanded SDOH items. Continued growth of Social Determinants of Health data collection — housing stability, food security, transportation, health literacy, social isolation.
  4. SPADE alignment. Continued cross-setting standardization via Standardized Patient Assessment Data Elements.
  5. Updated CMS guidance. The OASIS-E2 Guidance Manual supersedes the OASIS-E1 manual for all assessments completed on or after the effective date.

For full item-level detail, see What Changed in OASIS-E2: Item-by-Item Guide.

PDGM Payment Impact: What to Watch

The biggest financial risk in transitioning from OASIS-E1 to OASIS-E2 is unexpected PDGM payment-pattern shifts. Refined Section GG items can change how clinicians score functional impairment, which shifts patients between Low / Medium / High functional levels under PDGM — and that directly affects the 30-day payment amount.

During the first 60–90 days of OASIS-E2, agencies should:

  • Compare average PDGM payment per 30-day period to the 90-day pre-OASIS-E2 baseline
  • Identify clinicians whose functional impairment scoring shifts dramatically
  • Run focused QA on Section GG scoring during the first 30 days
  • Provide just-in-time feedback to clinicians on scoring drift

For real-time PDGM-aware scoring guidance, see Lime's OASIS-E2 ambient scribe.

Transition Plan: From OASIS-E1 to OASIS-E2

  1. Week -8: Capture baseline metrics (PDGM payment, error rates, time-to-completion)
  2. Week -6: Confirm EMR vendor OASIS-E2 form push timeline
  3. Week -4: Update written OASIS policies and QA rule sets
  4. Week -3: Begin clinician training on OASIS-E2 changes (see 90-day training plan)
  5. Week 0: OASIS-E2 effective date — clinicians complete first assessments with QA co-signing
  6. Weeks 1–4: Daily QA huddles, weekly PDGM payment monitoring
  7. Weeks 5–12: Move to weekly QA review; complete competency validation
  8. Week 13: Full independent practice; quarterly internal audits begin

For the complete agency rollout playbook, see OASIS-E2 Implementation Playbook.

Related OASIS-E2 Resources

OASIS-E1 vs OASIS-E2 — FAQ

What's the difference between OASIS-E1 and OASIS-E2?
OASIS-E2 is the next iteration of OASIS-E1, with refinements to functional assessment items (Section GG), cognitive and behavioral items, expanded Social Determinants of Health (SDOH) items, and continued IMPACT Act standardization across post-acute settings. The structural framework — five required time points, M-item architecture, PDGM payment mapping, and HH QRP submission requirements — remains intact. OASIS-E2 is an iterative update, not a wholesale rewrite, which means existing OASIS-E1 workflows can be updated incrementally rather than rebuilt.
When did OASIS-E1 take effect vs OASIS-E2?
OASIS-E1 took effect January 1, 2025, replacing the original OASIS-E (which was effective January 1, 2023). OASIS-E2 was scheduled by CMS to take effect in 2026 as the next iteration. Agencies should reference the CMS OASIS-E2 Guidance Manual and applicable transmittals for the exact effective date applicable to their assessment time points.
Can I keep using OASIS-E1 forms after OASIS-E2 takes effect?
No. Once OASIS-E2 is the active version per CMS guidance, all submitted assessments must be on the OASIS-E2 form. Most home health EMR vendors (HCHB, WellSky, MatrixCare, Axxess, DSL) push the form update automatically. Agencies that submit on the prior version after the effective date will receive submission errors and risk Quality Reporting penalties.
Will OASIS-E2 affect my PDGM payment?
Possibly. The PDGM mapping framework (clinical group + functional impairment level + comorbidity adjustment) is preserved in OASIS-E2, but refined Section GG functional items can shift functional impairment scoring patterns — which directly affects the 30-day payment amount. Agencies should monitor PDGM payment trends weekly during the first 60–90 days of OASIS-E2 to identify any unexpected payment shifts and respond quickly.

Transition to OASIS-E2 without payment leakage.

See Lime's OASIS-E2 Scribe