Common Part B Billing Mistakes in SNFs

Almost every Part B denial we see in a skilled nursing facility traces back to one of seven errors. The codes change. The MAC jurisdictions change. The LCDs change. The errors don't. After auditing 40+ new SNF onboardings over the last two years, the same pattern shows up in every building — regardless of EHR, ownership structure, or geographic region.

Below is the working list, ordered by frequency. For each one we cover what it looks like in PointClickCare, why it triggers a denial or takeback, and the operational fix. The goal isn't to memorize codes; it's to install a workflow that catches the error before the claim is submitted, not after the recoupment letter arrives.

1. Billing supplies during an active Part A stay

The single most common denial. PDPM consolidated billing absorbs nearly every supply during an active Part A benefit period — submit a Part B claim during that window and CMS rejects with a consolidated-billing edit. The fix isn't 'don't bill,' it's 'know the calendar.'

• Symptom: CARC 109 or 226, consolidated-billing reason codes
• Root cause: Billing workflow doesn't pull from the live Part A admission/discharge file
• Fix: Daily reconciliation of Part A census against the Part B claim queue; suppress any Part B build for a resident in an active Part A stay; resume billing the day Part A discharges (or exhausts)
• Reference: Medicare Part A vs Part B in SNFs

2. Missing or stale Standard Written Order

CMS revised the SWO rule in 2020 — one order can now cover all items, and the format requirements simplified. But the order still has to exist, has to be signed by the treating physician, and has to predate (or coincide with) dispensing. SWOs that arrive after the fact, lack a date, or were signed by a non-treating practitioner fail audit.

3. Unit-count errors against the HCPCS descriptor

Every HCPCS code has a unit definition baked into its descriptor. Bill against the wrong unit and you either underbill by 30× (catheters dispensed as 1 unit instead of 30) or overbill and trigger a medical-review edit. Enteral nutrition (per-100-calorie units), surgical dressings (per-square-inch), and nebulizer drugs (per-mg) are the worst offenders.

4. LCD-required diagnosis missing or wrong

Every Local Coverage Determination lists the ICD-10 diagnoses that establish medical necessity. A supply billed without one of those diagnoses on the claim denies as 'not medically necessary' — even if the underlying clinical condition is real and documented. Auditors don't go hunting through the chart for an implied diagnosis; the diagnosis has to be on the claim.

The fix is a pre-bill LCD validator: a checklist that confirms the claim's ICD-10s match the controlling LCD's covered list before the claim transmits. Our SNF Billing Guidelines walks through the LCDs that touch SNFs most often.

5. No Proof of Delivery on DMEPOS claims

PoD is the audit document. Beneficiary or authorized-designee signature, date of delivery, supplier name, item description. Missing any one and the claim is recoupable on review. The eMAR alone is not a PoD; the nurse charting is not a PoD; the delivery ticket without a signature is not a PoD.

Read more in How DME Claims Work in SNFs — section on SWO + PoD covers the exact packet format auditors expect.

6. Wrong, missing, or stacked modifiers

Modifiers tell the MAC what the line item means. The big four that go wrong in SNF Part B:

• KX — 'medical-necessity documentation on file' attestation. Required by most DMEPOS LCDs. Missing KX = denial.
• GA / GZ / GY — Advance Beneficiary Notice modifiers. Used incorrectly, they convert a payable claim into a write-off or a fraud flag.
• RT / LT — Laterality. Required on bilateral items billed as separate lines.
• NU vs. RR — Purchase vs. rental. Wrong choice = wrong reimbursement methodology applied.

7. No re-evaluation after Part A discharge

This is the silent revenue killer. A resident finishes their Part A days, and the building keeps providing the same supplies — catheters, dressings, nebulizer treatments — but nobody flips the billing flag from 'consolidated' to 'Part B billable.' Months go by. The supplies are dispensed, the documentation is fine, the resident is eligible, but no claims are ever submitted.

What 'fixed' actually looks like

The seven errors above are operational, not clinical. None of them require new headcount, new vendors, or new EHRs — they require a billing workflow that knows the SNF Part B rules at the code level and runs daily reconciliation against the live census. Burst-billed claims sit at a sub-3% audit-flag rate against an industry baseline closer to 25%, because the seven errors above are caught in the pre-bill scrub, not on the back end.

If you want to see your facility's current audit-flag exposure against your own 12-month claim history, book a no-cost claim audit. For deeper background on each rule, see How Part B Reimbursement Works and our Medicare Audit Defense service.