CPT code 40899: Unlisted mouth procedure, oral vestibule2026 Medicare rate & RVUs in California

CMS doesn’t publish an office rate for 40899 in California.

Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.

What 40899 covers

CPT 40899 is an unlisted procedure code for work involving the vestibule of the mouth when no listed CPT code describes the service. The oral vestibule is the space between the lips or cheeks and the teeth or gums. The code does not identify a particular technique or diagnosis, so the claim description should explain the procedure performed. Oral and maxillofacial surgeons and other clinicians performing oral procedures may report it. Before selecting it, compare the work with specific codes for services such as biopsy, lesion excision, or mouth reconstruction.

Medicare assigns physician fee schedule status C, or carrier priced: CMS publishes no national payment, and the Medicare Administrative Contractor sets payment for each claim. The contractor also sets the global period. For multiple procedures in one session, the highest-valued procedure is paid in full and other procedures at 50% under the stated Medicare multiple-procedure rule. Include claim details and clinical documentation that explain the unlisted service.

This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.

Where 40899 pays more and less in California

The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.

29 of 29 payment localities

How the 40899 rate is calculated

Each of 40899’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.

Payment rules and modifiers for 40899

The CMS indicators that decide how 40899 is paid alongside other services.

What modifiers do to the payment

When to use modifier 51

40899 compared with similar codes

How to choose

40808Mouth biopsyOral vestibule

40808 is the listed biopsy code for a mouth lesion. Use 40899 only when the procedure is not described by that or another specific code.

40810Mouth lesion excisionWithout repair

40810 is a listed excision code for a mouth lesion. Consider 40899 only when no listed code describes the work performed.

40819Frenum excisionLip or cheek fold

40819 is for excision of a lip or cheek fold. It is not a general substitute for other unlisted mouth procedures.

40840Mouth reconstructionAnterior vestibuloplasty

40840 is a listed mouth reconstruction code. Use it when its described service fits; reserve 40899 for work without a matching listed code.

Codes related to 40899

Related codes aren’t interchangeable: bill the code that matches the service performed.

Where these rates come from

FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.

CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027

Open CMS sourceHow we calculate rates