CPT code 77401 – Superficial and orthovoltage delivery code

Key takeaways

CPT code 77401 was deleted on January 1, 2026, so it is valid only for superficial or orthovoltage fractions delivered in 2025 or earlier.

From 2026, surface radiation therapy is reported with 77436 for planning, 77437 or 77438 for each delivery fraction, and add-on 77439 for ultrasound guidance.

The kV recorded for each fraction now decides the delivery code: 77437 at 150 kV or below, 77438 above 150 kV up to 500 kV.

The AMA bars planning, simulation, dosimetry, weekly management and megavoltage delivery codes alongside 77436-77439, so 2025 billing habits now cause bundling denials.

Pabau, the practice software we build, sends the claims your team codes to payers through Claim.MD. It tracks each response, so rejected 77401 lines are caught early.

CPT code 77401: a deleted superficial and orthovoltage delivery code

CPT code 77401 described radiation treatment delivery, superficial and/or ortho voltage, per day, and it is no longer valid for current dates of service. The AMA deleted it effective January 1, 2026. Its 2026 CPT errata and technical corrections carry the instruction to see 77436, 77437, 77438 and 77439 for surface radiation therapy instead.

CMS made the same change on the same date. Its code list update effective January 1, 2026 deletes 77401 from the radiation therapy services list. It also deletes Category III code 0394T, the code for high dose rate electronic brachytherapy applied to the skin surface.

The code is now historical. Use it only on claims for fractions delivered on or before December 31, 2025. Every superficial or orthovoltage fraction from January 1, 2026 onward is reported with the Surface Radiation Therapy codes below.

For those older claims, 77401 worked like this:

• Unit: one unit per treatment day, whatever the number of fields treated that day.
• Energy: superficial and orthovoltage work shared a single code, with no split by kV.
• Related services: planning, simulation, dosimetry and weekly management were typically reported with their own codes.

What replaced CPT 77401 in 2026

The AMA added a Surface Radiation Therapy subsection to Radiation Oncology for 2026. It defines surface radiation therapy as external radiation below 500 kV that limits penetration beyond the skin. Four codes now cover the delivery 77401 used to report, plus the planning around it.

Three changes matter most for coders. Delivery is counted per fraction rather than per day. Superficial and orthovoltage work now splits into two codes at 150 kV. Planning and field setting move into one code, 77436, built for this modality.

Older guidance that treats 77436-77439 as a separate device category billed alongside 77401 is out of date. The AMA instruction sends users from 77401 straight to these four codes, so they replace it outright.

Codes you cannot report with 77436-77439

The new family carries a long exclusion note, and it changes how a skin radiation course is billed. Under 77401, practices typically reported planning, simulation, dosimetry and weekly management with their own codes. The AMA parenthetical note now bars every code in the table below alongside 77436-77439.

Two pointers close the note. High-energy treatment of skin cancer with electrons, photons or gamma rays goes to 77402, 77407 or 77412. High dose rate radionuclide surface brachytherapy goes to 77767 or 77768.

The megavoltage codes changed for 2026 as well. The AMA now assigns 77402, 77407 and 77412 by treatment-delivery complexity, Level 1, 2 or 3, rather than by beam energy. 77406 is not a current delivery code, so any crosswalk that still lists it needs replacing.

Billing across the January 1, 2026 transition

The date of service decides which code set applies, not the date the course was planned or the claim was sent. Courses that crossed the new year are where most coding questions come from. The chart below follows a single fraction from its date of service to the code it takes.

• Dates of service through December 31, 2025: bill 77401 per treatment day, with the planning and management codes that applied at the time. Medicare claims still have to reach the MAC within 12 months of the date of service.
• Dates of service from January 1, 2026: bill 77437 or 77438 per fraction, chosen by the documented kV. Add 77439 once per course when ultrasound guidance placed the fields.
• Courses that crossed the new year: split the claim lines by date. December 2025 fractions go out as 77401, and fractions from January 2026 go out as 77437 or 77438.
• Planning for a split course: the code text is silent on 77436 for the 2026 part of a course planned under 2025 codes. Ask each payer before you bill it.
• Authorizations issued under 77401: payer handling is payer-specific. Confirm with each plan whether the existing authorization covers 77437 or 77438 before the next fraction, and keep the answer on file.

Documentation for surface radiation therapy claims

The 150 kV split between 77437 and 77438 makes the energy setting the first field a coder reads. Each fraction’s treatment record should show these elements.

• Energy setting: the kV used for that fraction, recorded as a number rather than a device brand or the letters SRT.
• Fraction and dose: the fraction number against the prescribed course and the dose delivered that day.
• Site and field: the anatomic site, specific enough to match the ICD-10 code, and the field size.
• Prescription: the dated, signed order from the treating physician that sets the treatment parameters.
• Ultrasound guidance: when 77439 is billed, a record of the ultrasound used to place the field.
• Planning record: the planning and field-setting work that supports 77436.

A record that says only SRT or superficial cannot show which delivery code applies. Fix it in the treatment note template with a required numeric kV field.

ICD-10 codes that support medical necessity for surface radiation therapy

Each payer sets the diagnoses it accepts in its own coverage policy, which is a core part of medical billing for radiation services. The codes below are the diagnoses most often documented for superficial and orthovoltage treatment of skin cancer.

Check the MAC’s local coverage documents and each commercial payer’s radiation oncology guideline before the first fraction. A benign lesion code, such as D23.- for other benign neoplasms of skin, needs explicit support in that policy before radiation is billed.

Medicare payment for 77436-77439

Medicare pays surface radiation therapy under the Physician Fee Schedule. CMS valued the new codes in the CY 2026 final rule. It then updated the practice expense values for 77436, 77437 and 77438 in a March 2026 correction notice.

Look up current payment amounts and RVUs in the CMS Physician Fee Schedule lookup tool. Rates vary by locality and by site of service, and they change with each annual update.

Common claim denials after the 77401 deletion

Most denials on superficial and orthovoltage claims in 2026 trace back to 2025 habits carried into the new codes. Each one has a fix you can build into your denial management workflow and pre-submission checks.

• 77401 on a 2026 date of service: the line fails because the code was invalid on that date, often with CARC 181. Recode it to 77437 or 77438 from the documented kV and resubmit.
• Wrong delivery code for the energy: 77437 billed above 150 kV, or 77438 billed at 150 kV or below. Read the kV in the treatment record before assigning the code.
• Excluded codes on the same claim: 77427, simulation or dosimetry billed alongside the new family. Expect these to deny as bundled, often with CARC 97, and remove them before submission.
• 77439 billed alone or per fraction: the add-on goes with 77437 or 77438 and is reported per course of treatment.
• Megavoltage and surface codes together: 77402, 77407 or 77412 billed with 77436-77439. The AMA note bars the pairing, so bill the family that matches the modality used.
• Diagnosis outside the payer’s policy: a medical necessity denial, usually CARC 50. Confirm the ICD-10 code against the payer’s guideline before the first fraction.

Knowing the billing denial codes behind each rejection lets the appeals team send the right documentation the first time. A clean claim also needs the fraction count, date of service and treating provider to match across the treatment record and the claim form.

How Pabau keeps surface radiation claims on track after the code change

After a code deletion, billing teams mostly fight two problems: claims built from old templates, and rejections nobody notices for weeks. Pabau keeps each claim and its payer response next to the patient record, so both problems show up in one place.

Your team enters the codes for each fraction, and Pabau’s claims management sends those claims to payers through Claim.MD, our US clearinghouse integration. It then tracks claim status and payer responses. A 2026 line still carrying 77401 comes back as a rejection your team can correct and resend.

Code selection stays with your coders. Pabau submits and tracks the claim data your team enters, which keeps corrected claims moving well inside the payer’s filing limit.

Track surface radiation claims after the code change

Pabau sends the claims your team codes to payers through Claim.MD and tracks each response, so rejected 77401 lines get corrected quickly. See how it works for radiation oncology practices.

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Conclusion

Treat 77401 as a code for 2025 dates of service only. The quickest protection is a hard stop in your charge entry or claim templates for any 2026 date of service that carries it. Follow it with a review of every course that crossed the new year.

The larger shift is financial. Planning, simulation, dosimetry and weekly management codes no longer sit alongside surface radiation delivery. A skin radiation course therefore produces fewer billable lines than it did in 2025. Update fee forecasts to reflect that, and settle split-course and authorization questions with each payer before you bill.

Book a demo to see how Pabau submits and tracks radiation oncology claims through Claim.MD, so corrected 2026 claims go out fast.

Continue your research

Want to understand how clearinghouse submissions work? Medical claims clearinghouse guide explains how claims move from practice to payer and where rejected surface radiation claims typically surface.

Need to reduce denial rates across your radiation oncology claims? Electronic remittance advice explained covers how to read ERA files and identify denial patterns by CARC code before they repeat.

Credentialing with payers before first billing? Getting credentialed with insurance companies walks through the enrollment steps required before surface radiation therapy claims will process for new radiation oncology providers.

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