Dermatology Medical Billing Guide: Mohs Surgery Coding & 2026 Documentation Changes

CMS tightened Mohs surgery documentation requirements in the 2026 Physician Fee Schedule Final Rule — if your dermatology practice's operative note templates haven't been updated to match, that's a real, current denial risk, not a hypothetical one.

Dermatology billing spans everything from routine skin checks to complex reconstructive procedures, but Mohs micrographic surgery carries some of the specialty's most detailed and frequently updated coding rules.

Mohs Surgery Coding Structure

CPT 17311 — First stage of Mohs surgery on the head, neck, hands, feet, or genitalia, including removal and interpretation of up to five tissue blocks. Billed only once per procedure.

CPT 17312 — Each additional stage at the same site, reported alongside 17311.

CPT 17313 / 17314 — The equivalent first-stage and additional-stage codes for trunk or extremity locations.

A defining rule of Mohs billing: the same physician has to act as both the surgeon performing the excision and the pathologist interpreting the tissue for the case to qualify for these codes — a split between two different providers for those roles doesn't meet the code definition.

The 2026 Documentation Change

CMS's 2026 Physician Fee Schedule Final Rule tightened documentation requirements for Mohs surgery, now requiring explicit block-count documentation for each individual stage specifically to prevent unbundling. Practices whose operative note templates don't capture block count per stage are at real risk of denials or post-payment audit findings under the updated requirements — this is a template fix, not a coding judgment call.

Billing Multiple Stages Correctly

Multiple instances of the additional-stage codes (17312, 17314) shouldn't be reported on separate claim lines — they should be totaled and billed as a single line item with the appropriate number of units, rather than listed stage-by-stage.

Modifier Requirements

Modifier 59 (or the more specific X-modifiers: XE, XS, XP, XU) is required on repair/closure codes billed alongside Mohs codes, and on any second lesion treated on the same date, to prevent those services from being automatically bundled and denied. It's worth noting the Mohs codes themselves (17311–17314) don't include wound repair — that's billed separately, with the appropriate modifier attached.

Documentation Checklist for Clean Mohs Claims

Confirmed same physician performed both excision and pathological interpretation

Explicit block count documented for each individual stage (2026 requirement)

Anatomic location clearly specified (head/neck/hands/feet/genitalia versus trunk/extremity determines which code family applies)

Repair/closure documented and coded separately with appropriate modifier

Get a free practice audit and we'll check whether your Mohs surgery documentation templates already reflect the 2026 block-count requirement.

Frequently Asked Questions

What changed in Mohs surgery billing for 2026? CMS's 2026 Physician Fee Schedule Final Rule now requires explicit documentation of the tissue block count for each individual stage, specifically to prevent unbundling.

Can two different providers split the surgeon and pathologist roles for Mohs billing? No — CPT 17311/17312 require the same physician to perform both the excision and the pathological interpretation.

Do Mohs surgery codes include wound repair? No — repair or closure is billed separately from the Mohs codes themselves, typically with a modifier to prevent automatic bundling.

How should multiple additional Mohs stages be billed on one claim? As a single line item totaling the appropriate number of units for 17312 or 17314, not as separate line items per stage.

What modifier is needed for a second lesion treated the same day? Modifier 59 or the more specific X-modifiers (XE, XS, XP, XU), to indicate it's a distinct procedural service rather than a duplicate.