You sit down to file a clean claim and a denial from last week comes back instead. The note is solid, the assessment happened, the family showed up. But the code on the superbill is wrong, or it's bundled, or it's missing a modifier. And now you're trying to figure out whether to refile, appeal, or just write it off.
If you've ever stared at CPT 92521 next to 92522, 92523, and 92524 and felt like they all look the same, you're not alone. These four evaluation codes are the most-confused codes in speech-language pathology billing. Picking the wrong one is one of the top causes of denied or downcoded claims.1
This guide walks through what each code actually covers, the rule that decides which one applies, the 92522 vs. 92523 trap that produces the most denials, and the documentation that holds up if an auditor ever asks why you billed what you billed.
The Four SLP Evaluation Codes at a Glance
Here's the short version of what each code covers:
- 92521 evaluates fluency. Stuttering, cluttering, and other disfluency-based disorders.
- 92522 evaluates speech sound production only. Articulation, phonology, apraxia, dysarthria.
- 92523 evaluates speech sound production plus language comprehension and expression. It includes everything 92522 does, with the language piece on top.
- 92524 is a behavioral and qualitative analysis of voice and resonance.2
All four are untimed, service-based codes. You bill them once per evaluation, no matter whether the session ran 45 minutes or two hours. That's different from the cognitive-communication codes (97129/97130), which are billed in 15-minute units, and it's a distinction worth keeping clear if you work across multiple disciplines.
One thing to clear up before we go further: people sometimes search "oral function evaluation cpt code" and land on 92524. The voice and resonance code does cover some oral function observation. But if you're billing for treatment of swallowing or oral function for feeding, that's 92526, which is a treatment code with a different scope. The 92521 through 92524 set is strictly for evaluation.
And here's the rule that drives every code selection decision in this set:
The code reflects what you actually assessed and documented, not the referring diagnosis.
That sentence does a lot of work, because most miscoding in this code set traces back to ignoring it.
CPT 92521: When You Evaluated Fluency Only
Bill 92521 when fluency was the entire scope of the evaluation. That means stuttering, cluttering, and related disfluency disorders, assessed on their own.
A typical 92521 evaluation note will include a speech sample analysis with disfluency counts (percentage of syllables stuttered is the common metric), a severity rating from a validated tool like the SSI-4, parent or teacher or self-report input on impact, and a description of how the disfluency affects communication and participation. If your note shows all of that and only that, 92521 is the code.
A common scenario: a pediatric SLP at a school-affiliated clinic evaluates a 7-year-old referred for stuttering. The SLP collects a speech sample, scores the SSI-4, talks with the parent about onset and family history, and observes the child in a structured conversation task. No formal language testing. That's 92521.
92521 can be billed on the same day as 92523 if you also conducted a complete, distinct speech sound and language evaluation and both are medically necessary.2 But the documentation has to clearly support two separate evaluations. Combining them by default, just because the family drove a long way and you wanted to be thorough, isn't a billing strategy. It's an audit invitation.
CPT 92522 vs. CPT 92523: The Most Common Coding Mistake
This is where the most money gets lost (and the most money gets clawed back). The 92522 and 92523 pair is the single biggest source of overbilling and CCI-edit denials in the SLP evaluation code set.1
Here's the cleanest way to hold the distinction:
- CPT 92522 covers speech sound production only. Articulation, phonological processes, motor speech (apraxia, dysarthria). If your evaluation didn't formally assess language comprehension or expression, this is your code.
- CPT 92523 covers speech sound production plus language comprehension and expression. It includes everything 92522 does. The language piece is what triggers the upgrade.
And here's the hard rule: you cannot bill 92522 and 92523 on the same date of service for the same patient. The CPT manual and the National Correct Coding Initiative (CCI) edits bundle them, because 92523 already contains 92522.3 Reporting both gets denied as duplication.
The mistake usually runs in one of two directions. Some clinicians default to 92523 for every evaluation because it sounds more comprehensive. If you only assessed articulation, that's overbilling, even unintentionally. Other clinicians bill 92522 when they also administered a language battery like the PLS-5 or CELF-5, which is undercoding the work they actually did.
One useful guardrail: Modifier 52 (Reduced Services). If you started a 92523 evaluation but only completed the speech sound portion (the kid melted down, you ran out of time, the parent had to leave), don't bill the full 92523. Append Modifier 52 to signal the service was reduced.4
Quick example. A pediatric SLP evaluates a 4-year-old referred for "speech delay." Articulation testing only, no language battery. That's 92522. If the SLP brings the child back the following week for the PLS-5, that visit isn't 92523 either, because the speech sound piece was billed previously. Language-only evaluations don't have a perfect single fit in this code set, so check 96105 and confirm payer policy before filing.5
CPT 92524: The Voice and Resonance Code
CPT 92524 covers behavioral and qualitative analysis of voice and resonance. The components you'd expect to see in the note: a perceptual voice rating (CAPE-V is the most common, GRBAS still in use), pitch and loudness range, resonance assessment, vocal hygiene history, observation of vocal behaviors during structured and unstructured tasks, and stimulability testing.
The boundary worth knowing: 92524 is the behavioral piece. It doesn't cover instrumental exams like flexible laryngoscopy, stroboscopy, or laryngeal EMG. Those have separate codes (92511, 92520, 31579, among others) and are typically billed by the otolaryngologist, not the SLP.
This is also where the "oral function evaluation cpt code" search confusion lands hardest. If you came to this article looking for an oral function code and you meant voice or resonance, 92524 is your code. If you meant treatment of swallowing or oral feeding function, that's 92526, which lives on the treatment side of the fee schedule.
A typical 92524 scenario: a private-practice SLP evaluates an adult elementary-school teacher referred after an ENT visit for vocal nodules. The SLP scores the CAPE-V, measures fundamental frequency and pitch range, reviews vocal hygiene, and runs stimulability tasks. Bill 92524. The laryngoscopy that prompted the referral is on the ENT's claim, not yours.
Same-Day Billing, Modifiers, and Documentation That Holds Up
Most of the denials in this code set aren't about picking the wrong evaluation code. They're about same-day rules, missing modifiers, and notes that don't support the code on the claim. Here's what to keep in front of you.
Same-day with 92507 (treatment). Medicare generally does not allow the same practitioner to bill 92507 and an evaluation code (92521 through 92524) on the same date of service without exceptional documentation supporting two genuinely distinct encounters.6 Some commercial payers permit the combination with Modifier 59 and a clear clinical rationale, but policies vary. Verify with the specific payer before you file. If you're guessing, you're going to be appealing.
Same-day across evaluation codes. 92521 plus 92523 is allowed when both are medically necessary and separately documented. 92522 plus 92523 is not, because they're bundled. 92521 plus 92524 is allowed (fluency and voice are independent scopes). When in doubt, ask whether each code stands on its own as a complete, distinct evaluation in the note.
Modifiers worth knowing for this code set:
- GN. Required on all Medicare Part B SLP claims. It tells the payer that services were delivered under a speech-language pathology plan of care.6 Forget it on a Medicare claim and the denial is automatic.
- KX. Required once the patient's annual therapy charges exceed the threshold (set at $2,410 for 2025).7 KX signals that services beyond the threshold are medically necessary.
- 52. Partial evaluation completed. Don't bill the full code if you didn't deliver the full service.
- 59. Distinct procedural service. It's the most-misused modifier in SLP billing. Use it only with documentation showing a genuinely separate service, because overuse is itself an audit trigger.1
A documentation checklist that defends any of these four codes:
- Standardized assessments named and scored. "Administered SSI-4, total score 22, severity moderate" is defensible. "Conducted fluency assessment" is not.
- Speech samples and clinical observations recorded, not summarized into adjectives.
- Functional impact on communication, participation, school, or work described concretely.
- Medical necessity for skilled SLP services made explicit. Not just what you did, but why this patient needed a licensed SLP and not a parent, a teacher, or an assistant.
- Treatment plan tied directly to the findings, with measurable goals.
One rule worth writing on a sticky note: write the eval note so a reader who has never met the patient can identify which of the four codes you billed without you telling them. If the documentation requires the code to make sense, the code isn't supported.
Pick the Code That Matches What You Actually Did
The four-code question comes down to a simple discipline: bill the code that matches what you assessed and documented, not what the patient was referred for. 92521 for fluency only. 92522 for speech sound production only. 92523 when language is also assessed. 92524 for voice and resonance. The same-day rules and modifiers add a layer of complexity, but they don't change the underlying logic.
And here's the quieter point: most denials in this code set aren't coding failures. They're documentation failures. Tighten the note, and the code defends itself.
Need SLP billing software that supports clean evaluation documentation? ClinicNote is a speech therapy EMR built with university clinics and private practice EMR users who bill these four codes every week. SOAP notes link directly to CPT and service codes, supervisors can review documentation in real time, and document completion verification flags gaps before claims go out. Get a demo and see how ClinicNote fits your evaluation workflow.
Sources
- https://www.medbridge.com/blog/slp-cpt-codes-how-to-optimize-your-billing-for-success
- https://www.asha.org/practice/reimbursement/coding/new-cpt-evaluation-codes-for-slps/
- https://medibillmd.com/blog/cpt-code-92522/
- https://www.sprypt.com/cpt-codes/92523
- https://www.sprypt.com/blog/cpt-codes-used-for-speech-therapy-evaluation
- https://www.asha.org/practice/reimbursement/medicare/slpcodingrules/
- https://gawendaseminars.com/faq/slp-billing-payment/