HCPCS Code A4361: Ostomy faceplate billing guide

Key Takeaways

HCPCS Code A4361 is a Level II supply code for an ostomy faceplate, billed per unit under Medicare Part B’s prosthetic device benefit.

Claims require a supporting ICD-10 diagnosis (Z93.3 colostomy status or Z93.2 ileostomy status) and valid physician order.

Modifier NU is the standard append for new ostomy faceplate supply; modifier RR applies only to rental equipment, not disposable supplies.

Keeping the physician order, ICD-10 diagnosis, and proof of delivery in one patient record, the kind of record-keeping practice management software like Pabau supports, lowers the risk of an avoidable denial.

Official descriptor: Ostomy faceplate, each.

HCPCS Code A4361 is a Level II supply code maintained by CMS for use on Medicare Part B DME claims. In other words, the “each” unit of service means every faceplate billed is counted one at a time. However, bundling multiple units into a single line without showing the correct quantity is a common documentation error that triggers audits.

In most cases, A4361 denials trace back to a missing ICD-10 diagnosis, a wrong modifier, or a quantity that goes over the monthly allowable without supporting medical necessity on file.

An ostomy faceplate (also called a baseplate or wafer) is the rigid or semi-rigid piece that sticks directly to the peristomal skin. It then connects to the ostomy pouch and forms a seal that protects the skin from effluent. Because faceplates are separate from the pouch itself, they are billed under their own HCPCS code.

The code sits within the A4361-A4438 ostomy supply range, which covers the full spectrum of ostomy pouching system parts. For example, billers working on HIPAA-compliant claims submission workflows for DME suppliers will regularly encounter A4361 when patients present with colostomy, ileostomy, or urostomy status.

A4361 code details at a glance

First, the table below captures the quick-reference details billers need before submitting an A4361 claim.

2025-2026 Medicare fee schedule for HCPCS Code A4361

Medicare allowable amounts for A4361 vary by DME MAC jurisdiction and geographic locality. Because CMS updates the fee schedule every year, the figures below reflect general ranges reported across jurisdictions for 2025-2026. Therefore, always confirm the current rate using the CMS fee schedule tool before submitting.

CMS fee schedule allowables for ostomy supply codes like A4361 change with geographic adjustments and yearly payment rule updates. As a result, suppliers must check the current allowable directly through the AAPC HCPCS code lookup or the official CMS fee schedule download before finalizing claims.

ICD-10 diagnosis codes used with HCPCS Code A4361

Every A4361 claim submitted to Medicare requires a supporting ICD-10 diagnosis that shows the patient’s ostomy status. Without a linked, payable diagnosis, the DME MAC will deny the claim for not having enough medical necessity documentation. Similarly, the same diagnosis-pairing rule applies to related ostomy supplies billed under A4367.

Then, use the status codes (Z93.x series) as the primary listed diagnosis when the patient has an established, working ostomy with no current complication.

In contrast, K94 series codes are the right choice when a complication is the reason for the encounter, and if that complication needs urgent surgical revision, the anesthesia is billed separately under 99140.

Finally, check the applicable codes against the current DME MAC LCD for ostomy supplies before submitting, since covered diagnoses may be refined at the jurisdiction level.

Applicable modifiers for HCPCS Code A4361

Modifier selection on A4361 claims is a steady source of rejections. The most common error is adding a rental modifier (RR) to a supply code. However, faceplates are single-use supplies, not rental equipment. As a result, applying RR tells the DME MAC that the supplier is treating a disposable item as durable equipment, which triggers an automatic rejection.

Check the relevant DME MAC LCD to confirm whether KX is required for your jurisdiction before submitting. For instance, some jurisdictions have made KX mandatory for all ostomy supply claims above a set quantity threshold.

Coverage criteria and quantity limits for A4361

Medicare Part B covers ostomy faceplates as medically necessary supplies for patients with a permanent or long-term ostomy. CMS passes coverage policy to DME MAC LCDs, which set out both the qualifying diagnoses and the quantities Medicare will pay for each month. Similarly, the same framework governs the urinary pouch billed under A4432.

• Physician/treating provider order: A written order from the treating physician or qualified non-physician practitioner is required before supply can be dispensed. The order must state the ostomy type, quantity authorized, and expected length of need.
• Proof of delivery (POD): The supplier must get and keep a signed delivery document showing the patient received the supplies. Electronic or paper POD is fine, but it must be produced on request during post-payment audits.
• Diagnosis documentation: The patient’s medical record must contain notes that show the ostomy status, matching the ICD-10 code submitted on the claim.
• Quantity limits: Medicare typically pays for up to a set number of faceplates per month based on the type of ostomy system. For example, a one-piece pouching system generally allows for a higher monthly quantity than a two-piece system, where the faceplate stays in place and the pouch is replaced on its own. Quantities above the stated limit require more medical necessity documentation.

In addition, practices using digital intake forms can automate the collection of physician orders, consent records, and clinical notes, which lowers the risk of missing documentation at the time of a DME MAC audit. This applies whether the original order came from a general practice that manages long-term ostomy care or from a surgical specialist.

Always confirm quantity limits against the jurisdiction-specific LCD, since DME MAC policies can vary.

How to bill HCPCS Code A4361 to Medicare

Clean A4361 claims follow a consistent workflow. Missing any step below is the main reason for initial denials, so running through this checklist before submission catches most errors early.

1. Get and file the physician order. Check that the order states the ostomy type, A4361 by description or code, quantity, and frequency, then file it in the patient record before dispensing.
2. Next, verify the patient’s ICD-10 diagnosis. Confirm the correct ostomy-status code (Z93.2, Z93.3, or Z93.6 as appropriate) is documented in the patient chart and matches what will appear on the claim.
3. Check the DME MAC LCD. Confirm the patient’s diagnosis is on the covered-diagnosis list for the correct jurisdiction. If the LCD requires modifier KX, document that coverage criteria are met.
4. Then, enter code A4361 with the correct quantity. Show the actual number of faceplates dispensed, and do not bundle multiple units into a single unit of service.
5. Add modifier NU. For new supplies, NU is the standard modifier. Also add KX if required by your DME MAC, but never add RR.
6. Next, get proof of delivery. Collect the signed POD before or at the time of delivery, and keep it in the claim file.
7. Submit the claim to the DME MAC through the correct DME MAC portal, and check that the NPI, taxonomy code, and supplier number are correct before submission.
8. Finally, monitor remittance and respond to denials. If denied, review the remark code. Common fixes include adding a missing diagnosis, correcting the modifier, or submitting supporting documentation for a quantity that went over the standard limit.

For example, the PGM HCPCS lookup tool offers a free reference for checking A4361 code details and linked modifier information before submission.

Keep your billing documentation organized

Practice management software like Pabau helps your team store physician orders, consent forms, and other patient records in one place, so documentation is easy to produce whenever a payer asks for it.

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Related HCPCS codes for ostomy supplies

HCPCS Code A4361 sits within a broader range of ostomy supply codes. Knowing the nearby codes, in turn, prevents co-billing errors and helps billers pick the right code when a patient uses a different system type.

These codes often appear together on the same claim when a complete pouching system is supplied. For instance, billers supporting facilities that use physical therapy EMR workflows for post-surgical ostomy care should know this full range.

The key difference between A4361 and A4375/A4380 is the system type. When a patient uses a one-piece pouching system, the faceplate and pouch are supplied together and billed under a single code (A4375 or A4380). In contrast, A4361 is used only when the faceplate is billed as a separate part, which happens with two-piece systems.

Billing A4361 alongside A4375 for the same patient in the same month without documentation of a system change will trigger a duplicate claim edit. Meanwhile, the surgical closure of an ostomy is billed separately under its own procedure code, such as 44227 for a laparoscopic enterostomy closure.

Common billing errors and how to avoid them

A4361 denials cluster around a few common error types. Each one can be caught early with a careful pre-submission review. Similarly, the same pattern shows up when peristomal skin breakdown adds a secondary diagnosis such as L26 to the claim.

Common A4361 denial triggers

• Missing or invalid ICD-10 diagnosis. Submitting A4361 without a covered ostomy-status diagnosis (Z93.2, Z93.3, Z93.6, or applicable K94 code) results in a medical necessity denial. Fix: check that the diagnosis is documented in the patient record and matches the claim before submission.
• Incorrect modifier (RR instead of NU). Applying the rental modifier RR to a disposable supply triggers an automatic edit. Fix: use NU for all new ostomy faceplate supplies, then check with the DME MAC LCD whether KX is also required.
• Quantity exceeds monthly allowable without documentation. Medicare quantity limits are set by DME MAC LCD, so supplying more units than the standard allowable without a documented medical necessity reason results in a partial payment or denial. Fix: get and file the treating provider’s written order that spells out the higher quantity and the clinical reason before dispensing.
• Missing proof of delivery. POD is a post-payment audit requirement, but many denials on review happen because POD was not collected at delivery. Fix: collect a signed delivery confirmation before or when the patient receives supplies, and keep it in the claim file for at least seven years.
• Wrong code for the system type. Billing A4361 for a patient on a one-piece system (who should be billed under A4375 or A4380) creates a claim mismatch against prior billing history. Fix: check the pouching system type from the physician order and the patient’s most recent clinical notes before picking the HCPCS code.

Practices managing a high volume of DME supply claims benefit from building this checklist into a standard pre-submission review. Likewise, this same discipline catches deleted or revised codes such as J1040 before they cause a rejection.

Conclusion

HCPCS Code A4361 is a simple supply code that becomes complicated fast when the required paperwork is missing by the time a claim reaches the DME MAC. Overall, the most consistent A4361 claims pair a valid Z93.x or K94.x diagnosis with modifier NU, a signed physician order, and a proof of delivery on file before submission.

Practice management software helps billing teams keep physician orders, diagnosis documentation, and delivery records organized in one place, so the paperwork is ready whenever a payer asks for it. Book a demo to see how Pabau can support your practice’s record-keeping.

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Frequently Asked Questions

More A4361 billing FAQs