CPT code 17315: Mohs surgery billing for additional tissue blocks

Key takeaways

CPT code 17315 is a Mohs micrographic surgery add-on code. It reports each additional tissue block after the first five processed within a single stage, on any anatomical site.

It must always be billed alongside a primary Mohs code. Use CPT 17311 for the head, neck, hands, feet, or genitalia, or CPT 17313 for the trunk, arms, or legs. Never bill 17315 as a standalone code.

The most common denial trigger is billing 17315 without a primary code. A close second is reporting units that do not match the block count in the operative report.

Pabau’s claims management software helps dermatology practices pair add-on codes correctly, flag mismatched block counts before submission, and reduce Mohs billing denials.

The American Medical Association designates CPT Code 17315 as an add-on code, meaning it cannot be billed independently. Its official descriptor: Mohs micrographic technique, each additional tissue block after the first five tissue blocks, any stage.

Two conditions must both be true before CPT Code 17315 applies:

• Block count: more than five tissue blocks are processed within a single stage of the procedure
• Primary code present: CPT 17311 or CPT 17313 has already been reported for that same stage, depending on the lesion’s anatomical site

Stage number does not matter for the block-count trigger, but it does decide which code 17315 pairs with. Suppose a surgeon processes eight blocks during a single stage on a patient’s back. The code billed for that stage covers the first five blocks, and CPT Code 17315 is reported three times for the rest. If that eight-block stage is the first stage, the parent code is 17313. If it is a later stage instead, the parent code is 17314, not 17313.

The Mohs surgery CPT code family: 17311 to 17315

CPT Code 17315 is one of five codes in the Mohs micrographic surgery family. Understanding where it sits within the family is essential before billing any Mohs case. The primary codes (17311 and 17313) anchor each claim; the add-on codes (17312, 17314, and 17315) are built on top of them.

The most common source of confusion is the distinction between 17314 and 17315. CPT 17314 is specific to the trunk, arms, or legs, and it applies to each additional stage after the first. CPT Code 17315 works differently. It applies to each additional block beyond the first five within a single stage, on any anatomical site. It pairs with whichever code, 17311, 17312, 17313, or 17314, was billed for the specific stage where the excess blocks occurred. Wrong code selection here consistently triggers payer edits.

When to use CPT 17315: Add-on code rules

CPT Code 17315 fires only when both conditions below are met. Meeting one of two is not enough, and unlike the primary codes, it is not limited to the first stage.

1. A primary code has already been reported for that stage. Head, neck, hands, feet, and genitalia use CPT 17311; trunk, arms, and legs use CPT 17313. The operative report must document the anatomical site explicitly, whichever code applies.
2. The block count for that stage exceeds five. The first five blocks in any given stage are already covered by the primary code. Report one unit of CPT Code 17315 for each block processed after those first five, in that same stage.

Primary code vs add-on code: 17311, 17313, and 17315

CPT 17311 and CPT 17313 are the foundations. Each covers the first five tissue blocks of a single Mohs stage. CPT 17311 applies to the head, neck, hands, feet, or genitalia, and 17313 applies to the trunk, arms, or legs. CPT Code 17315 stacks on top of whichever code, 17311, 17312, 17313, or 17314, was billed for that specific stage. It applies to every block beyond the five-block threshold. Consider a claim where the surgeon processed nine blocks in a single stage on a patient’s shoulder, assuming that stage is the first stage. The correct coding is 17313 x1 and CPT Code 17315 x4. If that nine-block stage were a later stage instead, the pairing would be 17314 x1 and CPT Code 17315 x4. Never report 17315 without a primary or additional-stage code on the same claim.

Medicare reimbursement rates for CPT code 17315 (2026)

Medicare pays different rates depending on where the procedure is performed. Non-facility settings (physician offices, standalone dermatology practices) receive a higher rate because the practice bears overhead costs. Facility settings (hospital outpatient departments, ambulatory surgery centers) receive a lower physician component rate because the facility bills separately for overhead.

According to CMS Physician Fee Schedule data, the 2026 indicative non-facility rate for CPT Code 17315 is approximately:

These figures are indicative and subject to annual MPFS adjustment. Always verify the current-year rates directly with CMS before quoting reimbursement internally. Commercial payer rates for CPT Code 17315 vary by contract and are typically higher than Medicare rates. Verify with each payer’s fee schedule or provider portal.

Dermatology practices tracking revenue per procedure benefit from claims management software. It flags cases where the reimbursed amount falls outside expected ranges for a given code, setting, and payer combination.

Medicare coverage criteria for Mohs surgery

Medicare covers Mohs micrographic surgery under coverage guidance published by CMS in Medicare Coverage Database article A53883, along with companion articles A57477 and A57767. These are maintained by the relevant Medicare Administrative Contractor (MAC). Coverage requires documented medical necessity, which generally means the tumor meets one or more of these criteria:

• Malignant histology confirmed (basal cell carcinoma or squamous cell carcinoma are the most common indications)
• Tumor location in a high-risk area or recurrent after prior treatment
• Aggressive histologic subtype (morpheaform, infiltrative, perineural involvement)
• Tumor size meeting threshold criteria per the coverage article (size thresholds vary by anatomical site)
• Patient immunocompromised or with high surgical risk requiring tissue conservation

The operative note must connect each of these factors to the patient’s specific presentation. A generic “medically necessary” statement without supporting clinical detail does not satisfy coverage requirements. Some MACs require the surgeon to document why standard excision was inadequate.

Prior authorization requirements for Mohs surgery vary by commercial payer. Medicare does not require prior authorization for Mohs procedures, but many commercial plans do. Verify with each payer before scheduling, particularly for UnitedHealthcare’s Mohs reimbursement policy and for Aetna. Document the authorization number in the patient’s record and on the claim.

ICD-10 codes used with CPT 17315

CPT Code 17315 must be paired with an ICD-10-CM diagnosis code that reflects the confirmed malignancy. Because 17315 can accompany either primary code, the diagnosis code should match whichever anatomical category applies. Use trunk, arm, or leg codes when paired with 17313, and head, neck, hand, foot, or genitalia codes when paired with 17311. Using a benign lesion code or an unspecified site code when a specific site is documented will trigger a payer edit.

Always select the most specific code available. If pathology confirms basal cell carcinoma of the right shoulder, code C44.611, not the unspecified trunk code. Specificity matters for medical necessity review, coverage compliance, and claim payment. Practices managing dermatology billing can use digital intake forms to capture anatomical site and clinical details at consultation. This reduces transcription errors that propagate into ICD-10 code selection.

Documentation requirements for Mohs surgery billing

Inadequate documentation is the leading cause of post-payment audits in Mohs surgery billing. A routine medical chart audit catches most of these issues before a payer ever sees the claim.

The operative report must support every unit of every CPT code reported on the claim. For CPT Code 17315 specifically, the record must demonstrate that the block count genuinely exceeded five within the stage where the add-on code was reported.

• Total number of stages performed: document each stage clearly, with start and completion notation
• Blocks processed per stage: every block in every stage must be individually enumerated. If eight blocks were processed in stage two, the report should state “eight tissue blocks processed during stage two”
• Anatomical site: specify the body region (e.g. “right posterior shoulder”) to support whichever primary code, 17311 or 17313, matches that site
• Surgeon-pathologist identity: Medicare requires that the operating surgeon also perform the pathological examination. Document that the Mohs surgeon interpreted the frozen sections
• Frozen section pathology results: record the margin status for each block at each stage
• Medical necessity rationale: connect the tumor characteristics (histology, size, location, prior treatment history) to the decision to perform Mohs surgery
• Reconstruction plan: if reconstruction was performed, document it separately. Repair codes are not included in the 17315 global package and must be supported by their own documentation. This includes a skin substitute graft code like CPT 15276 when tissue replacement is required.

Practices using structured patient records with procedure-specific note templates capture this data at the point of care. That reduces the scramble to reconstruct documentation during a payer audit. The dermatology EMR software a practice uses should make the Mohs operative note fields non-optional, not an afterthought.

Common billing errors and denials for CPT code 17315

The table below covers the denial patterns billing staff encounter most often with CPT Code 17315, along with the corrective action for each. A related mix-up is confusing this add-on family with standalone excision codes such as CPT 11402, which carry separate documentation requirements.

Denial management for Mohs claims is less about appeals and more about front-end claim scrubbing. Catching a block count error before submission takes 30 seconds. Appealing a denial after the fact takes weeks. The best practice management software for dermatology integrates claim editing rules that flag these specific coding relationships before the claim leaves the practice.

Streamlining Mohs surgery billing with practice management software

Mohs billing is structurally different from most dermatology procedures. The number of code units changes dynamically based on intraoperative findings. The block count is not fixed at scheduling, and the code pairing rules are strict. That combination creates a higher-than-average error rate when billing teams rely on manual code entry.

Practice management platforms designed for dermatology handle several of the failure points directly. When a billing team builds a charge from an operative note in skin clinic software, business rules can enforce code pairing automatically. 17315 cannot be saved without a primary Mohs code, 17311 or 17313, on the same encounter. The system can also calculate the correct number of 17315 units from the documented block count. It can flag ICD-10 codes whose body site does not align with the primary CPT code’s site requirement.

Documentation workflows matter equally. Surgeons often dictate or complete structured operative notes inside the practice management system rather than in a separate platform. When they do, the block count and anatomical site data populate directly into the charge capture workflow. That single-source-of-truth approach eliminates the transcription step where most block count errors originate. Practices interested in reducing documentation burden for complex surgical cases can explore how structured CPT coding workflows apply across different specialties. They can also review how other dermatology billing scenarios.

Payer-specific rules for Mohs surgery, including UnitedHealthcare’s Mohs reimbursement policy and individual MAC coverage articles, can be stored as billing rules within the platform. Prior authorization reminders then trigger for the right payers automatically. Rather than relying on a staff member to remember which commercial plans require auth for Mohs, the system flags the requirement at scheduling. It does this as soon as it detects the patient’s insurance plan. The compliance requirements that govern clinical documentation for these procedures are equally important to maintain systematically rather than manually.

Related CPT codes

• CPT code 17250 — Chemical Cauterization of Granulation Tissue
• CPT Code 17380 — Electrolysis epilation billing, modifiers, and reimbursement
• CPT code 17999 — Unlisted Integumentary Procedure
• CPT code 19083 — Ultrasound-guided breast biopsy

Reduce Mohs billing denials with smarter claim workflows

Pabau’s dermatology practice management platform helps billing teams pair add-on codes correctly, flag block-count and site mismatches before submission, and track denial patterns across payers. See how it works for skin cancer practices.

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Conclusion

CPT Code 17315 is a precise add-on code with two non-negotiable conditions. The stage must contain more than five tissue blocks, and a primary code, 17311 or 17313, must already be reported for it. Get either one wrong and the claim denies. The operative report is the single document that ties every requirement together, which makes documentation quality the most important variable in Mohs billing accuracy.

Pabau’s claims management software helps dermatology teams enforce add-on code pairing rules and verify block counts against documented operative data. This reduces the manual errors that drive Mohs denials. To see how it fits a dermatology billing workflow, book a demo with the Pabau team.

Continue your research

Need the full picture on the code 17315 pairs with in stage one? CPT code 17311 covers the first-stage primary code for head, neck, hand, foot, and genital Mohs cases.

Need structured forms that feed directly into billing workflows? Digital forms for practices explains how paperless intake and procedure documentation reduces transcription errors at the source.

Billing a later Mohs stage on the trunk or limbs? CPT code 17314 covers the additional-stage add-on code that often pairs with 17315.

Frequently Asked Questions