HCPCS Code A9900: Miscellaneous DME supply billing guide

Key Takeaways

HCPCS Code A9900 bills a DME supply, accessory, or service component that is already part of another coded item, not a stand-alone item on its own.

Medicare typically denies A9900 under ANSI/CARC reason code 97, treating the component as included in the payment for the primary DME item.

Use A9900 only for a component tied to an already-coded item; reach for A9999 instead when the supply itself has no HCPCS code at all.

Practice management software like Pabau helps medical aesthetics and wellness practices submit, track, and reconcile insurance claims, though DME suppliers billing Medicare Part B still need dedicated DME billing software.

HCPCS code A9900 is a Level II code CMS defines as a miscellaneous DME supply, accessory, and/or service component of another HCPCS code. It bills a component tied to durable medical equipment that already has its own code, not a stand-alone item.

Confusing it with HCPCS code A9999, the true miscellaneous catch-all, is the most common reason Medicare denies A9900 claims under CARC 97.

HCPCS Code A9900: definition and official CMS classification

Most A9900 denials come down to the same misunderstanding: billing it as a stand-alone item rather than what CMS built it to be, a supply, accessory, or service component tied to a DME item that already carries its own HCPCS code. That distinction is preventable once you know what the code is for.

HCPCS Code A9900 is a HCPCS Level II code maintained by the Centers for Medicare & Medicaid Services (CMS). Its official descriptor is: Miscellaneous DME supply, accessory, and/or service component of another HCPCS code. It sits within the A-series (A0000-A9999), which covers transportation services, medical and surgical supplies, and durable medical equipment.

A9900 is not the generic “not otherwise specified” catch-all some coders assume it is. That role belongs to HCPCS Code A9999 (Miscellaneous DME supply or accessory, not otherwise specified), used when a stand-alone supply has no dedicated code at all.

A9900 covers something narrower: a supply, accessory, or service component that supports a DME item already billed under its own HCPCS code, such as CPAP tubing, oxygen system connectors, or a fitting service tied to equipment that already has a code.

CMS releases HCPCS Level II updates on a rolling basis. Coders should always verify the current code set before billing. The PGM Billing lookup tool provides a free way to confirm A9900 remains active and unchanged in the current year’s release.

What A9900 covers: eligible supplies and use cases

A9900 applies to a supply, accessory, or service component that supports a DME item already billed under its own HCPCS code, not the primary item itself. This covers a range of scenarios in practice, including physical therapy practices billing brace or device accessories and occupational therapy practices billing adaptive equipment components. Common examples include:

• Replacement tubing, connectors, or fittings for a covered DME device that are billed separately from the primary item
• A setup, delivery, or fitting service tied to equipment that already carries its own HCPCS code
• Minor accessories supplied alongside a primary covered item that have no dedicated code of their own
• Maintenance or adjustment services performed on previously supplied, separately coded equipment

For A9900 to apply, the primary DME item it supports must still meet CMS’s definition of durable medical equipment:

• Designed for repeated use
• Primarily medical in nature
• Appropriate for home use
• Not useful to someone who is not ill or injured

A9900 is not appropriate for consumable, disposable, or single-use items that belong in other code categories. It is also not appropriate when the component itself has a specific HCPCS code, or when no code exists at all for a stand-alone supply, since that is when A9999 applies instead.

Good medical documentation workflows reduce the temptation to reach for the wrong miscellaneous code.

When to use A9900 vs. specific HCPCS codes

The single most common error with A9900 is confusing it with A9999, or using it for items that already have a specific HCPCS code. Payers audit miscellaneous and component codes more closely than specific codes, and using A9900 incorrectly almost always results in denial under ANSI/CARC reason code 97 or a request for additional documentation.

Before billing HCPCS Code A9900, confirm two things: that the item is genuinely a component of an already-coded DME item, and that no more specific component code exists. Search the current HCPCS Level II code set using the AAPC HCPCS code lookup. Document the search in your records, as some payers request evidence of it.

Medicare coverage and reimbursement for A9900

Medicare Part B does not have a nationally published fee schedule rate for A9900, and in practice most A9900 claims are denied rather than paid as a separate line item. Medicare Administrative Contractors (MACs) typically deny A9900 under ANSI/CARC reason code 97: payment for the component is considered already included in the allowance for the primary DME item it supports.

CMS does not maintain a National Coverage Determination (NCD) specific to HCPCS Code A9900. Coverage of the underlying, primary DME item is governed by the relevant Local Coverage Determination (LCD).

Suppliers should check the applicable MAC’s LCD for the primary item to understand whether its components, accessories, or service elements are bundled into that payment. The CMS fee schedule lookup can help verify any published payment rates that may apply to the primary code.

Medicaid and commercial payer policies

State Medicaid programs set their own DME coverage policies independently from Medicare. Whether a state Medicaid program separately reimburses a component billed under HCPCS Code A9900 depends entirely on that state’s fee schedule and coverage rules. Some states treat these components as bundled into the primary item regardless of MAC guidance.

Commercial payers are similarly variable. Many follow Medicare LCD guidance as a baseline but apply their own coverage restrictions. Some commercial payers require pre-authorization for any miscellaneous or component code. Billers working with patient care management across multiple payers should document payer-specific A9900 policies in their internal billing references, as requirements can shift with contract renegotiations.

Documentation requirements for A9900 claims

Component and miscellaneous codes attract higher scrutiny than specific HCPCS codes. Documentation for A9900 claims must do two things: establish that the component is medically necessary, and link it clearly to the primary, already-coded DME item it supports. Missing either increases denial risk significantly.

Core documentation requirements include:

• Written order from a treating physician that identifies the item by name, quantity, and the medical condition requiring it
• Statement of medical necessity explaining why the specific component is needed for the patient’s condition and treatment plan
• Reference to the primary DME item’s HCPCS code that the component supports, since A9900 is billed alongside an already-coded item
• Confirmation that no more specific HCPCS code applies to the component itself (some payers require a written statement from the biller or supplier)
• Prior authorization approval number (when required by the payer or MAC jurisdiction)
• Proof of delivery signed by the beneficiary or authorized representative
• Detailed item description including manufacturer name, model number, and function

Organized HIPAA-compliant record-keeping is not optional for A9900 claims. Payers may request documentation up to several years after the claim date during audits. Suppliers using digital intake forms can capture and store structured documentation at the point of care, making retrieval faster when payer requests arrive.

Simplify claims and billing documentation with Pabau

Practice management software like Pabau helps medical aesthetics and wellness practices submit, track, and reconcile insurance claims, and capture structured documentation with digital intake forms, instead of juggling spreadsheets.

Book a demo

How to bill A9900: step-by-step claim submission

Submitting an A9900 claim follows the same CMS-1500 form process as other HCPCS Level II DME claims, with additional steps to link the component to its primary, already-coded item. A structured approach reduces the likelihood of missing a required field.

1. Confirm the item is a component of an already-coded DME item, not a stand-alone supply. Search the current year’s HCPCS Level II code set for the primary equipment’s code. If the item genuinely has no code at all and no link to another coded item, use A9999 instead. Document your search result.
2. Obtain a valid written order. The treating physician must provide an order that identifies the item, quantity, and the relevant diagnosis code (ICD-10-CM) supporting medical necessity.
3. Obtain prior authorization if required. Contact the MAC or commercial payer before supplying the item. Some payers require prior authorization for all miscellaneous or component HCPCS codes.
4. Complete the CMS-1500 form. Enter A9900 in field 24D (Procedures, Services, or Supplies) and reference the primary item’s HCPCS code in the claim notes. Add the appropriate modifier in field 24D modifier column if applicable. Enter the relevant ICD-10-CM diagnosis code(s) in fields 21A-L and link them to the service line in field 24E.
5. Attach a narrative description. Some MACs and commercial payers require a written narrative attached to or submitted with the claim describing the item in detail. Check payer-specific requirements.
6. Submit with proof of delivery. Include the signed delivery confirmation. Electronic submission via EDI 837P is standard; attach documentation per payer instructions.
7. Track the claim and respond promptly to requests. A9900 claims are frequently denied under CARC 97 or trigger Additional Documentation Requests (ADRs). Dedicated DME billing software that flags pending responses reduces the risk of timely filing denials on resubmissions.

Good EHR integration between clinical documentation and billing workflows helps ensure the physician’s order, diagnosis codes, and supply description are consistent across the claim before submission. Inconsistencies between the clinical record and the claim form are a common audit trigger for component and miscellaneous codes.

Common billing errors and denial reasons for A9900

A9900 claims are denied more frequently than claims using specific HCPCS codes, most often under CARC 97 because payers treat the component as already included in the primary item’s payment. Most other denials fall into a small number of predictable categories.

Tracking denial patterns by payer, particularly how often claims are denied under CARC 97 versus other reasons, helps practices refine their A9900 workflow over time. Practices using robust medical practice management tools can run reports on denial rates by payer, which surfaces which insurers require extra documentation steps before initial submission.

Using medical dictation tools to capture physician narrative at the point of care closes most of the missing documentation that drives A9900 denials.

A9900 and HCPCS modifiers

Modifiers are frequently required when billing HCPCS Code A9900 under Medicare. The applicable modifier depends on the MAC’s LCD policies and the specific coverage situation. Common modifiers that may apply:

Modifier applicability depends on payer-specific guidelines. Verify the correct modifier against the relevant MAC’s LCD and the payer’s billing manual before submission. Practices that streamline their practice billing processes typically build modifier checklists for each payer into their standard DME intake workflow.

Related HCPCS codes for miscellaneous DME supplies

A9900 sits within a broader ecosystem of HCPCS codes for DME supplies, accessories, and components. Before defaulting to A9900, check these commonly referenced codes in the A-series and E-series, including A9999 for stand-alone supplies with no code of their own.

Practices managing a broad DME supply inventory benefit from structured coding reference systems. Linking supply items to their preferred HCPCS codes in a central reference reduces reliance on manual lookups and minimizes accidental use of A9900 when a specific code, or A9999, applies instead.

Conclusion

For the intake and documentation side of that process, digital forms software like Pabau’s can help practices capture structured physician orders and medical necessity statements at the point of care, though DME suppliers billing Medicare Part B still need dedicated DME billing software for the coding and claims side itself.

If your practice handles broader insurance billing beyond DME, practice management software like Pabau brings claims and billing into one system. Book a demo to see it in action.

Continue your research

Billing lower extremity orthoses? The billing guide for L2999 covers the same specific-code-first documentation principle DME suppliers need for A9900.

Handling home health certifications? The G0180 billing guide walks through Medicare’s certification requirements for home health DME and services.

Coding ostomy supplies? See the billing guide for A4427 for another example of a specific supply code that pre-empts a miscellaneous one.

Frequently asked questions