What Are the CPT Codes for FESS?
Functional endoscopic sinus surgery (FESS) is billed using a family of CPT codes ranging from 31254 through 31298, each representing a procedure on a specific sinus or anatomic structure performed through an endoscopic approach. In the 2026 CPT code set, these codes are organized by the sinus operated on (ethmoid, maxillary, sphenoid, frontal) and whether the procedure involves the initial surgery or a revision. Each FESS code is billable per side, meaning bilateral procedures require modifier 50, and multiple sinus procedures performed in the same session are billable when the operative note documents distinct work on each sinus.
Code range: CPT 31254 through 31298 covers ethmoidectomy, maxillary antrostomy, sphenoidotomy, frontal sinusotomy, and frontal sinus exploration, each with separate codes for initial and revision procedures.
Bilateral billing: FESS codes are unilateral. When the surgeon operates on both sides, append modifier 50 for bilateral procedure. Medicare reimburses bilateral FESS at 150% of the unilateral rate (100% + 50%).
Bundling with diagnostic endoscopy: CPT 31231 (diagnostic nasal endoscopy) is bundled into all FESS codes. Do not bill 31231 separately when FESS is performed in the same session.
FESS CPT Code Reference Table
| CPT Code | Procedure | Sinus | Initial or Revision |
| 31254 | Ethmoidectomy, anterior | Ethmoid | Initial |
| 31255 | Ethmoidectomy, total | Ethmoid | Initial |
| 31256 | Maxillary antrostomy | Maxillary | Initial |
| 31257 | Maxillary antrostomy with tissue removal | Maxillary | Initial |
| 31259 | Maxillary antrostomy with balloon dilation | Maxillary | Initial |
| 31267 | Maxillary antrostomy with tissue removal (revision) | Maxillary | Revision |
| 31276 | Frontal sinus exploration | Frontal | Initial |
| 31287 | Sphenoidotomy | Sphenoid | Initial |
| 31288 | Sphenoidotomy with tissue removal | Sphenoid | Initial |
| 31290 | Frontal sinus exploration (Draf IIb/III) | Frontal | Revision/Extended |
| 31298 | Ethmoidectomy, revision | Ethmoid | Revision |
This table covers the most commonly billed FESS codes. The full range includes additional codes for specific techniques and combined procedures. Each code is reported per side, and the operative note must document which sinuses were addressed and what was done in each. For how diagnostic nasal endoscopy (CPT 31231) relates to FESS billing, see our CPT 31231 overview.
FESS Bundling and NCCI Edits
FESS coding errors cost ENT practices more revenue than almost any other procedure category, and the majority of those errors involve bundling. Here are the rules that matter most.
31231 is always bundled into FESS. Diagnostic nasal endoscopy (31231) is included in every FESS code. If the surgeon performs a diagnostic endoscopy and then proceeds to FESS in the same session, only the FESS code is billed. Billing 31231 alongside any FESS code triggers an NCCI edit and the diagnostic code will deny.
Multiple FESS codes are billable in the same session when different sinuses are addressed. An ethmoidectomy (31254) and a maxillary antrostomy (31256) performed in the same session on the same side are separately billable because they involve different sinuses. No modifier 59 is needed because these are not bundled pairs.
Ethmoidectomy codes 31254 and 31255 cannot both be billed on the same side. 31254 is anterior ethmoidectomy and 31255 is total ethmoidectomy. If the surgeon performs a total ethmoidectomy, bill 31255 only. Billing both 31254 and 31255 on the same side in the same session is an NCCI conflict.
Revision codes require documentation of prior surgery. Codes like 31267 (maxillary revision) and 31298 (ethmoid revision) require the operative note to state that a prior procedure was performed on that sinus and that the current surgery addresses recurrent or residual disease. Using a revision code without documented prior surgery triggers audit flags.
In our experience matching ENT providers with billing partners, the bundling error between 31231 and FESS codes is the single most common denial we see on sinus surgery claims. The diagnostic endoscopy is inherent to the FESS approach and cannot be billed separately, but billing teams that are not ENT-specific frequently submit both codes because they see two procedures in the operative note.
FESS billing is where ENT practices lose the most revenue to coding errors: bundled diagnostic endoscopies, missed bilateral modifiers, and revision codes submitted without prior surgery documentation. A billing partner with ENT-specific coding expertise catches these before they become denials. ENT Billing Services matches your practice with vetted billing companies, free.
How Do You Bill Bilateral FESS?
All FESS codes are unilateral by definition. When the surgeon performs the same procedure on both sides in the same session, the claim carries the FESS code once with modifier 50 appended. Medicare reimburses bilateral procedures at 150% of the unilateral allowed amount: 100% for the first side and 50% for the second side.
Some commercial payers require a different approach: two line items with modifiers RT (right) and LT (left) instead of a single line with modifier 50. The billing team must know which method each payer accepts, because submitting the wrong format either leaves money on the table (single line when the payer expected two) or triggers a duplicate denial (two lines when the payer expected modifier 50).
For a practice performing 20 bilateral FESS cases per month, the difference between correctly billing bilateral and missing the second side is tens of thousands of dollars per year in lost reimbursement. The operative note must clearly state that the procedure was performed bilaterally. If the note describes work on only one side, the modifier is not supported and the second side will not pay. For ENT practices that also bill laryngoscopy procedures, the same bilateral modifier rules apply to paired-side nasal and sinus procedures.
FESS Documentation for Clean Claims
These six documentation elements must appear in the operative note for every FESS claim to hold on audit.
1. Identify each sinus operated on by name. State ‘anterior ethmoidectomy,’ ‘maxillary antrostomy,’ ‘sphenoidotomy,’ or ‘frontal sinusotomy’ explicitly. Do not use general language like ‘sinus surgery was performed.’
2. Document the side. State right, left, or bilateral for each sinus addressed. Modifier 50 or RT/LT requires laterality in the note.
3. Describe what was done in each sinus. Name the technique: tissue removal, polyp removal, bony partition removal, antrostomy creation, or balloon dilation. Each code corresponds to a specific intervention.
4. State whether this is initial or revision surgery. Revision codes require documentation that a prior procedure was performed on the same sinus and that the current surgery addresses recurrent or residual disease.
5. Document the medical necessity. Link the procedure to the diagnosis: chronic sinusitis (J32.x), nasal polyps (J33.x), or another supported ICD-10 code. The diagnosis must match the sinus addressed.
6. Note any additional procedures performed in the same session. If septoplasty (30520), turbinate reduction (30140), or other nasal procedures are performed alongside FESS, each must be documented separately to support separate billing. For ENT practices that frequently bill PE tube placement alongside sinus procedures, clear documentation of each procedure prevents bundling denials.
Common FESS Billing Mistakes
Across the billing companies we vet for ENT practices, these five errors account for the majority of FESS revenue loss.
Billing 31231 with FESS. Diagnostic nasal endoscopy is bundled into every FESS code. Billing it separately denies every time. This is the most common FESS billing error.
Missing bilateral modifier 50. Bilateral FESS submitted without modifier 50 pays for one side only. At 150% reimbursement for bilateral, the missing modifier leaves 50% of the second side’s payment uncollected.
Billing 31254 and 31255 on the same side. Anterior and total ethmoidectomy are not separately billable on the same side. If a total ethmoidectomy was performed, bill 31255 only.
Using revision codes without prior surgery documentation. Revision codes pay higher than initial codes but require documented prior surgery on the same sinus. Submitting a revision code without that documentation creates an audit finding.
Vague operative notes. An operative note that says ‘FESS performed bilaterally’ without naming each sinus and describing the work done in each does not support the individual CPT codes billed. Each code requires specific documentation.
Frequently Asked Questions
What is the CPT code for FESS?
FESS is billed using a family of codes from 31254 through 31298, not a single code. Each code represents a specific sinus procedure: ethmoidectomy (31254, 31255, 31298), maxillary antrostomy (31256, 31257, 31259, 31267), sphenoidotomy (31287, 31288), and frontal sinusotomy (31276, 31290). The code billed depends on which sinus was operated on.
Can you bill 31231 with FESS?
No. CPT 31231 (diagnostic nasal endoscopy) is bundled into all FESS codes under NCCI edits. The diagnostic endoscopy is inherent to the FESS approach and cannot be billed separately when FESS is performed in the same session. This is the most common FESS billing error.
How do you bill bilateral sinus surgery?
Append modifier 50 to the FESS code to indicate bilateral procedure. Medicare reimburses bilateral FESS at 150% of the unilateral rate. Some commercial payers require two line items with RT and LT modifiers instead. The operative note must document that the procedure was performed on both sides.
Can you bill multiple FESS codes in the same session?
Yes, when different sinuses are addressed. An ethmoidectomy (31254) and a maxillary antrostomy (31256) performed in the same session on the same side are separately billable. However, 31254 (anterior ethmoidectomy) and 31255 (total ethmoidectomy) cannot both be billed on the same side.
What is the difference between initial and revision FESS codes?
Initial FESS codes (31254, 31256, 31276, 31287) are used when the surgeon operates on a sinus for the first time. Revision codes (31267, 31298) are used when a prior procedure was performed on the same sinus and the current surgery addresses recurrent or residual disease. The operative note must document the prior surgery.
Does FESS require prior authorization?
Most commercial payers require prior authorization for FESS. The authorization request must include the specific CPT codes planned, the diagnosis codes, imaging results (typically a CT sinus), and documentation of failed medical management. Prior authorization rules vary by payer and by plan, so verification is required for each case.
Next Steps
For diagnostic nasal endoscopy billing and how it interacts with FESS, see our CPT 31231 overview.
For laryngoscopy billing alongside sinus procedures, see our CPT 31575 guide.
Ready to stop losing FESS revenue to coding errors? Get matched with an ENT billing partner who knows the sinus codes.
FESS is the highest-volume surgical procedure in most ENT practices, and every coding error on a FESS claim costs real money: a missed bilateral modifier, a bundled diagnostic endoscopy, or a revision code without documentation. ENT Billing Services matches your practice with vetted billing companies that specialize in ENT coding. Free quotes, all 50 states, rates starting at 2.95%.
