A resident arrives with a Medicare Advantage card. Your billing coordinator confirms active enrollment through the Medicare portal and clears the admission. Six weeks later, a CO-15 denial comes back — missing prior authorization. The plan required SNF-specific prior auth before day one. No one requested it, because everyone assumed confirming enrollment was the same as confirming coverage.
It is not.
Medicare Advantage enrollment and Medicare Advantage SNF coverage authorization are two different verifications. They come from two different sources. Facilities that treat them as one step are not making an occasional error — they are running a verification process that structurally produces CO-15 denials on every HMO admission where the authorization was not explicitly confirmed.
This post covers the specific verification steps SNF billing teams need for every HMO and Medicare Advantage admission: what to check, in what order, what to document, and what to do when authorization cannot be confirmed before the resident arrives.
Why HMO Eligibility Verification Works Differently in Skilled Nursing
Traditional Medicare Part A runs on federal rules that apply uniformly across every facility and every beneficiary. If a resident completed a qualifying inpatient hospital stay, has Part A benefit days remaining, and requires skilled care, coverage is predictable. Eligibility verification confirms known facts against a federal system.
Medicare Advantage plans are private insurance products. They use Medicare as a funding base but set their own rules for network participation, prior authorization requirements, and approved-day limits. Two residents presenting with Medicare Advantage cards from the same insurer may have entirely different authorization requirements depending on which specific plan each enrolled in.
The difference is structural: traditional Medicare verification is a lookup. HMO and Medicare Advantage verification for SNF admission is a negotiation with a utilization management department that controls whether coverage applies to your facility at all. In 2025, 54% of eligible Medicare beneficiaries — 34.1 million people — are enrolled in Medicare Advantage (Source: KFF Medicare Advantage in 2025: Enrollment Update and Key Trends). For most SNFs, that means the majority of new admissions now require the more complex HMO/MA verification process. Facilities running the same single-step workflow for both payer types are not running an efficient process — they are running a denial factory on a delay.
The Two-Step Verification Most SNFs Collapse Into One
Here is the mistake most SNF billing teams make with HMO admissions: they confirm the resident has active insurance and treat that as clearance. One step, one check, admission approved.
That single step tells you the resident has a plan. It tells you nothing about whether your facility is in-network for that plan, whether a prior authorization exists, what level of care was approved, or how many days the plan will pay for. Every one of those answers requires a second, separate contact that most billing teams never make.
Step 1 Confirm MA Plan Enrollment and Plan Identity
Check the resident’s Medicare Beneficiary Identifier through the Medicare portal or your verification system. Confirm active enrollment in a Medicare Advantage plan and identify the specific plan name, plan ID, and plan type.
Plan type is not administrative detail — it drives the entire verification pathway. The types SNF billing teams encounter most are HMO (strict in-network requirement, prior auth mandatory before admission), PPO (broader network access, prior auth still required for SNF stays), and D-SNP (Dual Eligible Special Needs Plan). D-SNP residents are enrolled in both Medicare Advantage and Medicaid. They require two parallel verification tracks — one for the MA plan, one for Medicaid — before any admission proceeds. Completing only the MA side for a D-SNP resident leaves half the coverage picture unconfirmed.
Step 2 Confirm Plan-Specific SNF Coverage Authorization
Contact the plan’s utilization management department — not the general member services line, which cannot authorize coverage — and confirm three things before any admission commitment is made: that your facility is in-network for this specific plan, that prior authorization is in place for a skilled nursing level of care, and that you have the full authorization record in hand.
In-network confirmation is not automatic. A resident enrolled in a UnitedHealthcare Medicare Advantage plan does not mean your facility contracts with that specific UnitedHealthcare product. Out-of-network admissions under HMO plans are not covered without an explicit exception authorization.
Prior authorization is required for skilled nursing facility stays by 99% of Medicare Advantage plans (Source: KFF Medicare Advantage in 2025: Premiums, Out-of-Pocket Limits, Supplemental Benefits, and Prior Authorization). This is not an edge case for certain plan types or certain regions. It is the standard across the MA market.
Hard Truth: If your HMO verification workflow ends when you confirm the plan is active, you have not verified coverage. You have confirmed the resident has insurance. Those are different things, and SNF billing teams that have not separated them will keep generating CO-15 denials regardless of how quickly they run the first check.
What to Capture During the Prior Authorization Process
Prior authorization for an SNF admission is not a yes/no approval. It is a specific set of fields that govern billing for the entire stay. Missing any one of them at admission means chasing them down after the resident is already in the bed, when the window for correction is narrower and the claim risk is already live.
When contacting the plan’s UM department, capture and document every field below before the admission decision is made:
- Authorization number. Every claim submission requires it. It cannot be added retroactively in most cases, and its absence is the direct cause of CO-15 denials. Log it at the time of the call — not at the time of billing.
- Approved level of care. The authorization must explicitly state skilled nursing facility care. If the approval language is ambiguous, call back before the admission proceeds.
- Authorized number of days. The plan approves a specific day count — not an open-ended stay. Days billed beyond the authorized count, without a renewed authorization, will be denied regardless of the resident’s clinical status.
- Authorization start date. A resident admitted before the auth start date is admitted without coverage, even if a valid authorization exists for dates that follow.
- Authorization expiration date. This field gets the least attention and causes the most mid-stay denials. The expiration date is the date by which the facility must submit a concurrent review request or the authorization lapses. Log it in a shared calendar the day the auth is obtained.
- UM reviewer contact information. Name, direct phone number, and fax number for the utilization management reviewer. This is a different contact from general provider services and is required for every concurrent review request throughout the stay.
In 2024, Medicare Advantage insurers fully or partially denied 4.1 million prior authorization requests — a 7.7% denial rate across all MA prior auth submissions (Source: KFF Medicare Advantage Insurers Made Nearly 53 Million Prior Authorization Determinations in 2024). The authorization record captured at the initial contact is the primary evidence in every appeal.
For payer-by-payer verification requirements at admission, see pre-admission eligibility verification requirements by payer across Medicare Part A, Medicaid, and Medicare Advantage/HMO.
The Concurrent Review Cycle What Happens After the Auth Is Approved
Getting prior authorization approved is not the end of the HMO verification process. It is the beginning of a coverage management obligation that runs until the resident is discharged.
Medicare Advantage and HMO plans use concurrent review — an ongoing utilization management cycle where the plan’s clinical reviewers assess whether the resident continues to meet medical necessity criteria for skilled nursing care. Review cycles vary by plan, typically running every 5 to 14 days for an active SNF stay. If the facility misses a review request, submits clinical documentation late, or allows the current authorization to expire without initiating a renewal, the plan terminates coverage retroactively to the last approved date. No advance notice. No gradual wind-down. The coverage stops at the expiration date, and the facility discovers it at claim submission.
This is not how traditional Medicare coverage ends. Traditional Medicare lapses when benefit days run out or when the resident no longer meets skilled care criteria. HMO coverage lapses when the facility fails to manage its concurrent review obligations on the plan’s schedule. It is an administrative failure, and it has nothing to do with the resident’s clinical status.
Four operational changes prevent it:
- Track every MA and HMO authorization expiration date in a shared calendar — not only in the billing system, where the problem surfaces at claim submission instead of five days before it matters.
- Set a renewal request trigger 5 to 7 business days before the expiration date. If the request is denied, the facility needs time to file an expedited appeal before coverage actually terminates.
- Assign the business office manager as the concurrent review owner for every active HMO stay. Concurrent review is an active-stay coverage management responsibility — not a billing function.
- Document every concurrent review contact: date, reviewer name, updated authorization number, and new expiration date.
The framing shift that matters most: the prior authorization is not the finish line for HMO/MA eligibility verification. It is the starting gun for a concurrent review process that runs the length of the stay.
See the three-stage SNF eligibility verification workflow for how concurrent review fits into the broader pre-admission, mid-stay, and post-denial verification structure.
What to Do When Authorization Cannot Be Confirmed Before Admission
Not every referral arrives with clean prior authorization in place. A hospital discharge planner calls Friday afternoon. The resident needs placement by Monday. The MA plan’s UM department has not responded to the authorization request.
This is the moment where most SNF billing teams default to Option 4: admit and hope the authorization comes through retroactively. It is not a written policy. It is the outcome of having no written policy — and it generates denials as reliably as any other broken process.
Three options exist. Every SNF should have a written protocol that specifies when each applies.
- Option 1 — Hold admission pending authorization. Communicate to the referral source that the facility cannot confirm an admission date until the plan confirms coverage. This is the cleanest financial outcome. The competitive risk is real: hospital discharge planners route to the first facility that can give a confident yes, and holding pending auth may cost the referral. That is a business decision — but it is a decision, not a default.
- Option 2 — Admit under a written private-pay agreement with a conversion clause. The resident is admitted as a private-pay patient. A written agreement signed before admission specifies that if MA authorization is obtained retroactively for the dates of service, billing converts to the plan. If authorization is denied, the resident or responsible party is financially liable. This agreement must be executed before the resident arrives.
- Option 3 — Decline the referral. The correct choice when the facility is confirmed out-of-network for the resident’s specific MA plan, when a prior authorization request has already been denied once for this admission, or when the clinical documentation is insufficient to support a skilled care authorization request.
The absence of a written protocol for unconfirmed HMO authorization is not a policy gap. It is a revenue policy by default. When no protocol exists, every unresolved authorization becomes an admit-and-hope situation and denials become the predictable output of a process with no decision point.
For more on how admit-under-uncertainty defaults drive revenue loss, see how eligibility sequencing errors cost SNFs revenue.
HMO Eligibility Verification Checklist for SNF Billing Teams
A working reference for the verification workflow above. Assign the checklist by role the fields that need to be completed before admission must be owned before admission.
At Referral Intake Admissions Coordinator
- Plan type identified: HMO, PPO, D-SNP, or C-SNP
- Facility in-network status confirmed for this specific plan
- Prior auth request initiated with plan UM department not general member services
- If D-SNP: Medicaid eligibility verification initiated as a parallel track
Before Admission Business Office Manager
- Authorization number logged in resident record
- Approved level of care confirmed -- must specify skilled nursing facility care explicitly
- Authorized number of days documented
- Authorization start date confirmed against planned admission date
- Authorization expiration date entered into shared concurrent review calendar
- UM reviewer name, direct phone number, and fax number documented
Active Stay -- Business Office Manager
- Concurrent review request submitted 5 to 7 business days before auth expiration
- Updated authorization number and new expiration date documented on renewal
- Any change in approved level of care reflected in billing before next claim submission
Frequently Asked Questions: HMO Eligibility Verification for Skilled Nursing Facilities
Yes, and it applies to virtually every plan. According to KFF's 2025 Medicare Advantage benefits analysis, 99% of MA enrollees are in plans that require prior authorization for skilled nursing facility stays. That figure is consistent across HMO, PPO, and Special Needs Plan types. Admitting an MA resident without confirmed prior authorization in place is the direct cause of CO-15 denials not a billing error, not a coding error, but a verification error made before the resident arrived.
Medicare Advantage is the federal program umbrella. HMO is one plan type within that umbrella, alongside PPO, D-SNP, and C-SNP. For SNF billing, the verification requirements are similar across MA plan types: all require in-network confirmation, all require prior authorization, and all use concurrent review to manage coverage during the stay. The specific authorization steps, approved-day limits, and review schedules vary by plan and insurer.
Concurrent review is the ongoing utilization management process HMO and MA plans use to assess whether a resident continues to meet medical necessity criteria for skilled nursing care. Reviews occur throughout the stay -- typically every 5 to 14 days -- and the facility must respond to review requests and renew authorizations before they expire. Missed review requests and expired authorizations result in retroactive coverage termination with no advance notice from the plan.
CO-15 is the denial code for a missing or invalid authorization number. In SNF billing, it means a claim was submitted for an HMO or MA resident without a confirmed prior authorization on file for the dates billed. CO-15 denials are the direct billing consequence of a verification process that treated MA enrollment as coverage confirmation rather than running the separate authorization check that actually governs SNF payment.
At referral intake not at admission. Most MA and HMO plans take 24 to 72 hours to process an SNF prior authorization request, and some require additional clinical documentation from the referring hospital before issuing a decision. Waiting until the day of admission eliminates the time needed to respond to a denial, file an expedited appeal, or execute a private-pay agreement before the resident arrives.
A D-SNP Dual Eligible Special Needs Plan is a Medicare Advantage plan designed for residents enrolled in both Medicare and Medicaid. D-SNP admissions require two parallel verification tracks: one for the MA plan (prior auth, in-network confirmation, approved level of care and days) and one for Medicaid (active enrollment status, level-of-care authorization, coordination of benefits). Running only the MA track for a D-SNP resident leaves the Medicaid coverage unverified -- and when the MA authorization covers a limited number of days, unverified Medicaid coverage means no confirmed billing path for the remainder of the stay.
Who This Is For
LTC Apps is built for skilled nursing facilities where the billing team is managing HMO and Medicare Advantage verifications manually — across separate payer portals, with authorization records logged in spreadsheets or sticky notes, and concurrent review tracked informally or not at all.
This is not the right fit if your facility needs a full physician-facing clinical EHR, or if your payer mix is exclusively traditional Medicare and Medicaid with no MA or HMO volume.
What Happens After You Request a Demo
- A member of the LTC Apps team reaches out within one business day to schedule a 30-minute live walkthrough.
- The demo focuses on the modules most relevant to your facility — eligibility verification, admissions, or both.
- Pricing specific to your facility size and module selection is on the table before the call ends.
No extended implementation timeline — most facilities are live on their first module within 2 to 4 weeks. No minimum facility size. If you are mid-contract with another vendor, a parallel evaluation now means you are ready to switch at contract end without making a rushed decision under time pressure.
Stop Building Denials Into Your HMO Admissions Process
If your facility admits Medicare Advantage residents and your verification workflow ends at confirming enrollment, you are generating preventable CO-15 denials on every HMO admission where the authorization was not explicitly confirmed. That is not a billing problem. It is a process design problem and it has a direct fix.
LTC Apps was built for skilled nursing facilities that need eligibility verification, admissions, and billing workflows running in one integrated platform not distributed across a billing coordinator’s browser tabs.
