7 Home Health Coding Errors Costing Agencies Revenue in 2026

This article identifies seven home health coding errors that are actively costing agencies revenue in 2026, what each one costs per episode, and the operational fix for each.

The Centers for Medicare and Medicaid Services (CMS) released an updated Patient-Driven Groupings Model (PDGM) Grouper software package effective April 1, 2026, with revised clinical group assignments and a revised unacceptable principal diagnosis table.

 That update followed the CY 2026 Home Health Prospective Payment System Final Rule, which recalibrated case-mix weights, updated Low Utilization Payment Adjustment (LUPA) thresholds, and revised comorbidity adjustment subgroups across the model (CMS Home Health PDGM). The aggregate result is an estimated 1.3% decrease in Medicare payments to home health agencies for 2026.

In this environment, home health coding errors that were financially manageable in prior years now carry greater per-episode cost. An incorrect primary diagnosis does not merely reduce payment for one claim. It assigns the entire 30-day period to the wrong PDGM clinical group. A missed comorbidity does not trigger the adjustment the patient's clinical complexity warrants.A late Notice of Admission (NOA) triggers a proportional payment reduction calculated as the number of days late divided by 30 of the period payment, deducted directly from the final claim payment.

The seven errors documented below are not isolated mistakes from individual coders. They are structural failures that appear repeatedly across home health agencies, regardless of size or Electronic Health Record (EHR) platform. Each section identifies where the failure originates, what it costs, and what the operational correction requires.

For a comprehensive view of how home health coding and Outcome and Assessment Information Set (OASIS) documentation interact under PDGM, agencies should review the Complete Guide to Home Health Coding and OASIS Review in 2026.

Key Takeaways

• CMS released PDGM Grouper v07.1.26 on April 1, 2026 with a revised unacceptable principal diagnosis table. Agencies validating ICD-10 primary codes against a pre-April 2026 grouper are using an outdated table and may not detect grouping failures before submission.
• The FY 2026 ICD-10-CM code set brought changes effective April 1, 2026, including Excludes1-to-Excludes2 revisions in key categories. A further 184 new diagnosis codes take effect October 1, 2026. EMR systems not updated to reflect these changes produce compliance errors without flagging them.
• The CY 2026 Final Rule updated comorbidity adjustment subgroups. Secondary diagnoses that did not qualify for adjustment under prior-year rules may now qualify, and agencies that have not reviewed their comorbidity capture workflows against the updated subgroups are leaving legitimate revenue unclaimed.
• When the NOA is not submitted within 5 calendar days of the start of care date, Medicare reduces the period of care payment by the number of days late divided by 30. Against the backdrop of the aggregate 1.3% payment decrease, this proportional reduction is more material now than in prior years. It is consistently a workflow failure, not a knowledge failure (CMS Medicare Benefit Policy Manual, Chapter 7, Section 10.4). 
• Face-to-face encounter documentation requirements expanded in 2026 to include a broader set of practitioners. Documentation must identify and support the specific practitioner type who performed the encounter.
• Most home health coding errors are not caught at the individual claim level. They are caught in patterns across denial reports, PEPPER data, or Medicare Administrative Contractor reviews, by which point multiple episodes have already been underpaid or denied.

Error 1: Primary Diagnosis Not Assigned to a Valid PDGM Clinical Group

Under PDGM, the primary ICD-10-CM diagnosis determines which of 12 clinical groups the 30-day period is assigned to. CMS maintains an accepted primary diagnosis list for each group. If the submitted primary diagnosis does not appear on that list, the claim is classified as an Unacceptable Diagnosis (UD) and returned to the agency before any clinical review occurs.

Where It Originates

Two patterns produce this error consistently. First, coders select a symptom code from the R00-R99 range as the primary diagnosis because the underlying condition is not yet confirmed in the physician documentation. Second, coders carry forward the hospital discharge diagnosis without reviewing whether that condition is the primary reason for home health services. Under PDGM, the primary diagnosis must reflect the specific clinical reason for skilled care at this episode, not the acute condition that preceded admission.

CMS Grouper v07.1.26, effective April 1, 2026, updated the unacceptable principal diagnosis table. Agencies that have not updated their grouper software to the April 2026 release are validating primary codes against a table that no longer reflects current CMS specifications. A code that passed grouper validation in March 2026 may generate a UD designation under the revised table.

Financial and Compliance Consequence

A UD designation results in a Return to Provider (RTP), delaying payment for the full 30-day period. The clinical group error also means the case-mix weight is incorrect, which affects reimbursement for the entire episode once the claim is corrected and resubmitted.

Operational Correction

• Validate every primary ICD-10 code against the CMS PDGM grouper before claim submission, not after.
• Confirm EHR and billing software vendors updated grouper logic to v07.1.26 as of April 1, 2026.
• Flag symptom codes from R00-R99 as a required quality assurance (QA) checkpoint at Start of Care (SOC) before the coder finalizes the primary diagnosis.

Escalation Level: Immediate : Any claim where the primary diagnosis triggers a UD or RTP must be corrected and resubmitted before the episode billing cycle closes. Do not batch these corrections.

Error 2: Underspecified ICD-10 Codes

PDGM requires coding to the highest level of specificity supported by the clinical documentation. Unspecified codes are valid ICD-10 entries, but they carry lower case-mix weights than their specific counterparts and increase audit scrutiny from Medicare Administrative Contractors (MACs). The FY 2026 ICD-10-CM code set, which includes changes effective April 1, 2026, revised Excludes1 notes to Excludes2 in several categories relevant to home health, including multiple sclerosis combinations and long-term opioid use with substance use diagnoses.

Where It Originates

Coders default to unspecified codes when physician documentation does not explicitly state the level of specificity the ICD-10-CM classification requires. For example, physician notes document diabetes without specifying type or complications, so the coder assigns the unspecified diabetes code rather than querying for clarification. The second pattern is EMR systems that have not been updated to the April 2026 ICD-10-CM code set, which means some codes that were previously coded as Excludes1 combinations may now be legitimately combined as Excludes2 pairs without triggering an edit error.

The October 1, 2026 ICD-10-CM update will bring 184 new diagnosis codes (CMS ICD-10). Episodes that begin before October 1 using a current code may require updates when billed after that date if the assigned code is revised, replaced, or deleted in the October update.

Financial and Compliance Consequence

Under PDGM, the primary ICD-10 diagnosis determines clinical group assignment and the associated case-mix weight. A more specific code may map to a different clinical group than an unspecified code for the same condition, affecting the episode payment (CMS Home Health PDGM). CMS accepts unspecified codes as valid submissions when documentation does not support specificity, which means coding accuracy gaps at this level do not generate claim denials. They generate underpayment without a visible trigger for internal review (ICD-10-CM Official Guidelines for Coding and Reporting FY 2026). 

Operational Correction

• Build a specificity checklist into the coding workflow: Does this code identify laterality, severity, and etiology where the ICD-10-CM classification requires it?
• Confirm EHR systems have been updated to the April 2026 ICD-10-CM Excludes revisions and begin preparing for the October 2026 code updates now.
• Establish a clinical query process between coders and clinical staff for diagnoses where documentation does not support the specificity the code set requires.

Escalation Level: Short-term : Specificity errors rarely generate a denial on their own. They surface in PEPPER outlier data and denial pattern reviews. Agencies should run a 90-day specificity audit against their highest-volume clinical groups and identify the diagnostic categories where unspecified codes are most concentrated.

‍

Error 3: Incorrect Timing or Admission Source Entry

PDGM payment groups include two variables that are determined entirely by intake data, not clinical documentation: timing (early versus late period) and admission source (community versus institutional). A wrong entry in either field assigns the episode to a different payment group, independent of how accurately the rest of the claim is coded.

Where It Originates

Timing errors occur when the first 30-day period is correctly classified as early but subsequent periods are mislabeled or when the SOC date entered in the billing system does not match the clinical record. Admission source errors occur when institutional admission history is not verified against discharge documentation at intake, and the agency defaults to community without confirming whether the patient had a qualifying institutional stay within the prior 14 days.

Financial and Compliance Consequence

Institutional source episodes typically reimburse higher than community source episodes in the same clinical group. Misclassifying an institutional patient as community results in underpayment for the episode. The reverse, classifying a community patient as institutional, results in an overpayment that becomes a repayment obligation when identified in a Medicare Administrative Contractor (MAC) review.

Operational Correction

• Build an admission source verification step into the intake workflow that requires review of discharge paperwork before the billing record is created.
• Add a SOC date cross-check between the clinical record and the billing system as a pre-submission QA item.
• Confirm that the billing system's period timing logic is accurately tracking early versus late classification across multi-period patients.

Escalation Level: Immediate : Institutional-versus-community misclassification that results in overpayment must be identified and corrected before the MAC identifies it. Self-identified overpayments reported voluntarily carry significantly lower compliance risk than overpayments discovered in audit.

Error 4: Face-to-Face Documentation Gaps

Medicare requires a face-to-face encounter with a qualifying practitioner to certify a patient's eligibility for home health services. The encounter must occur within the required timeframe relative to the SOC date and must be documented in a way that supports the clinical basis for home health eligibility. CMS expanded the list of qualifying practitioner types for the 2026 plan year to include physicians, nurse practitioners (NPs), physician assistants (PAs), and clinical nurse specialists, in addition to the previously qualifying types.

Where It Originates

Face-to-face denials consistently trace to two documentation failures: the encounter occurred outside the required timeframe, or the documentation does not establish the connection between the encounter findings and the patient's need for skilled home health services. The expanded practitioner eligibility in 2026 creates a new compliance gap for agencies that have not updated their intake documentation templates to capture and confirm the specific practitioner type.

Face-to-face documentation is one of the most frequently cited denial reasons in MAC reviews. The failure is almost never that the encounter did not occur. It is that the documentation does not connect the clinical findings to the homebound status determination and the need for skilled care.

Financial and Compliance Consequence

A face-to-face documentation failure can result in denial of the entire episode claim, not only a single visit. Because the face-to-face encounter is a condition of payment under 42 CFR Section 424.22, a deficient encounter document affects every claim in the episode.

Operational Correction

• Establish a face-to-face verification checkpoint at SOC that confirms the encounter date, the practitioner type, and that the documentation connects encounter findings to the homebound determination.
• Update intake documentation templates to capture the specific practitioner type performing the encounter, consistent with the 2026 expanded eligibility rules.
• Include face-to-face documentation review as a required item in the pre-billing QA checklist.

Escalation Level: Immediate : Any episode where the face-to-face encounter documentation is incomplete or outside the required timeframe should be flagged before billing. Submitting with a known face-to-face gap and receiving a denial requires an appeal process that costs significantly more staff time than a pre-submission correction.

Error 5: OASIS and ICD-10 Coding Misalignment

PDGM requires OASIS documentation and ICD-10 coding to support the same clinical picture. The OASIS functional scoring establishes the functional impairment level, and the ICD-10 primary diagnosis establishes the clinical group. Together, they determine the HIPPS code and the episode payment. When OASIS responses and coding decisions contradict each other, Medicare Administrative Contractors treat the mismatch as a documentation flag that can trigger additional review or denial.

Where It Originates

The most consistent pattern is GG0130 and GG0170 functional scores that indicate a lower impairment level than the coded primary diagnosis would clinically suggest. A patient coded for severe gait abnormality whose GG0170 mobility score indicates independence in ambulation presents a clinical contradiction that reviewers identify systematically. The second pattern is M-item coded responses that do not align with the narrative clinical notes, particularly for wound and skin conditions.

The CY 2026 Final Rule recalibrated functional impairment levels and their associated case-mix weights. Misalignment between OASIS functional scoring and the coded clinical group now carries greater financial consequence under the recalibrated model than it did under prior weights.

Financial and Compliance Consequence

A functional scoring mismatch that places a patient in a lower impairment level than the clinical record supports reduces the case-mix weight for the episode. Under 2026 recalibrated weights, the reimbursement gap between adjacent functional impairment levels in the same clinical group can be substantial.

Operational Correction

• Compare OASIS functional scoring against the primary diagnosis at SOC and recertification before the coding record is finalized.
• Include an OASIS-to-code crosswalk in the pre-billing QA process to confirm that the functional impairment level coded in the OASIS supports the case-mix group the primary diagnosis produces.
• Train clinical staff that GG0130 and GG0170 scores must be based on documented observed performance, not patient self-report.

Escalation Level: Short-term : OASIS-coding misalignment errors are rarely isolated to one episode. When identified, agencies should conduct a retrospective review of the prior 60 days of SOC and recertification assessments for the same clinician or the same diagnosis category to determine whether the pattern is systemic.

Error 6: Missed Comorbidity Adjustment Opportunities

Under PDGM, secondary diagnoses that qualify under CMS-defined comorbidity subgroup pairs trigger a Low or High comorbidity adjustment that increases the episode payment. A Low comorbidity adjustment requires one qualifying secondary diagnosis. A High comorbidity adjustment requires two or more diagnoses from qualifying subgroup interactions. The CY 2026 Final Rule updated the comorbidity adjustment subgroups. Secondary diagnoses that did not qualify for adjustment under prior-year rules may now qualify, and diagnoses that previously triggered adjustment may have been reclassified.

Where It Originates

Secondary diagnoses are documented in physician records but not carried into the home health billing record because no one on the clinical or coding team reviewed the full physician history at intake. The second pattern is secondary diagnoses coded to an unspecified level that does not meet the specificity threshold for the qualifying comorbidity pair. Diabetes with complications, for example, qualifies for comorbidity adjustment when coded to the appropriate specificity; the unspecified diabetes code does not.

Financial and Compliance Consequence

A missed Low comorbidity adjustment represents lost revenue on every episode where the qualifying diagnosis was present but not coded. Across a patient census with a high proportion of complex patients, the cumulative impact of systematic comorbidity undercapture is significant. Agencies that have not reviewed their comorbidity capture workflows against the 2026 updated subgroups are operating on the assumption that last year's qualifying diagnoses are still the complete picture.

Operational Correction

• Run a comorbidity checklist against each patient's physician records at SOC and recertification to identify secondary diagnoses that may qualify for adjustment under the 2026 updated subgroups.
• Review the updated CY 2026 comorbidity adjustment subgroup list against the agency's most common patient profiles to identify which secondary diagnoses warrant heightened capture attention.
• Ensure secondary diagnoses are coded to the level of specificity required for comorbidity adjustment, not to unspecified codes.

Escalation Level: Monthly : Comorbidity capture rate should be tracked monthly against the expected rate for the agency's clinical group distribution. A comorbidity capture rate significantly below the expected benchmark for the patient population indicates a systemic gap rather than isolated missed codes.

Error 7: No Pre-Submission QA Process

Most home health agencies have some form of quality review. The structural failure is not the absence of review. It is review that operates retrospectively, on a sampled basis, after claims have already been submitted. Retrospective sampled QA identifies error patterns after they have produced denials or underpayments. It does not prevent individual claims from going out wrong.

Where It Originates

Pre-submission QA is absent most often in agencies where coding and billing are treated as sequential handoffs rather than integrated workflows. The coder finalizes the ICD-10 record and passes it to billing without a structured checkpoint that compares the coded claim against the OASIS documentation, the physician orders, and the current PDGM grouper output. When this checkpoint does not exist, the claim goes out reflecting whatever errors were present when coding was completed.

The PDGM Grouper v07.1.26 update on April 1, 2026 is a concrete example of why a current-version grouper validation step must be part of every pre-submission workflow. Agencies that added grouper validation to their QA process after the 2020 PDGM implementation but did not verify that their vendor updated to v07.1.26 may be running validation against a superseded table.

Operational Correction

• Establish a pre-submission QA checklist that requires, at minimum: primary diagnosis validated against PDGM Grouper v07.1.26, OASIS functional scores cross-checked against narrative notes, face-to-face documentation confirmed present and within the required timeframe, and NOA submission date confirmed within 5 calendar days of SOC.
• Distinguish concurrent QA, completed before the claim is submitted, from retrospective QA, completed after the remittance returns. Both serve a purpose, but concurrent QA is the primary revenue protection mechanism.
• Review QA error logs weekly by coder, clinical group, and error type to identify systemic patterns rather than treating each finding as an isolated correction.

Escalation Level: Immediate : If the agency does not currently have a concurrent pre-submission QA process, building one is the single highest-priority operational change. Every other correction in this article is more effective when it operates inside a structured pre-submission review.

Summary: 7 Coding Errors and Their Escalation Level

How External Clinical Coding Review Addresses These Errors

For home health agencies where in-house coding staff are managing high chart volumes, keeping pace with mid-year PDGM grouper updates, ICD-10 code set changes, and OASIS-E2 instrument requirements simultaneously, the structural gap that allows these errors to persist is almost always a pre-submission review capacity problem rather than a knowledge problem. The coding team knows the rules. The workflow does not allow time to apply them consistently to every chart before it reaches billing.

An external clinical coding review function addresses this gap by providing a concurrent review layer between coding completion and claim submission. Every chart is reviewed against the current PDGM grouper version, current OASIS instrument requirements, and the specific claim's face-to-face and admission source documentation before the claim goes out. The review layer also generates coder-level and clinical-group-level accuracy data that makes systemic error patterns visible before they accumulate into denial cycles.

The Bottom Line

Home health coding errors under PDGM are not random. They follow predictable patterns that originate in specific workflow gaps: grouper software that is not current, intake processes that do not verify admission source, coding decisions that are not checked against OASIS documentation, and pre-submission review that does not exist or operates too late to prevent the error from reaching the claim. The 2026 environment, with recalibrated case-mix weights, updated comorbidity subgroups, a revised unacceptable diagnosis table, and mid-year ICD-10 code changes, increases the financial consequence of each of these gaps.

Agencies that treat home health coding accuracy as a daily operational discipline rather than a periodic audit function are the ones that maintain clean claim rates when the regulatory environment tightens around them.

How Red Road Supports Home Health Coding Accuracy

The agencies with the lowest home health coding denial rates are not necessarily the ones with the most experienced coders. They are the ones with the most structured pre-submission checkpoint. A 15-minute concurrent review of the primary diagnosis against the grouper, the OASIS functional score against the narrative note, and the face-to-face documentation against the SOC date catches the majority of the errors described in this article before they cost the agency revenue.

The grouper update on April 1, 2026 is not a minor administrative change. Agencies whose EHR vendors did not push the update automatically may still be running validation on an outdated table and will not know a claim will RTP until the remittance comes back. OASIS-coding misalignment follows a similar pattern — it is rarely caught by claim scrubbers, which check coding rules rather than clinical logic. It surfaces in Additional Documentation Request (ADR) responses, by which point the episode has already been paid at the wrong rate.

Red Road's home health coding services provide ICD-10 certified coders and Registered Nurse clinical reviewers who validate every chart against the current CMS standard before billing. Red Road has coded more than 2.5 million charts and reviewed more than 2 million charts at a consistent 98% accuracy rate. The review process includes primary diagnosis validation against PDGM Grouper v07.1.26, OASIS-to-code crosswalk checks, comorbidity capture review against the 2026 updated subgroups, and face-to-face documentation confirmation on every episode.

Coding accuracy, on-time completion, and error rates by type are tracked and reported weekly and monthly. When a systemic error pattern appears, the root cause is identified and reported to the agency before it reaches the volume that attracts MAC attention.

Explore how Red Road's home health coding services support coding accuracy and audit readiness.

This content reflects CMS guidance and regulatory standards as of 27 July 2026. Agencies should verify current requirements against the most recent CMS transmittals and MAC bulletins, and consult their legal and compliance advisors for guidance specific to their operations.