CPT code 90899 is one of the most misunderstood codes in behavioral health billing — and also one of the most necessary when you’re delivering care that the CPT book hasn’t fully caught up to yet. It exists for a simple reason: psychiatric and behavioral care evolve faster than the code set. When a provider delivers a legitimate psychiatric service with no specific code assigned, 90899 is the mechanism for seeking reimbursement.aapc+2
Used carefully, 90899 can capture real clinical work that would otherwise go uncompensated. Used loosely — without the right documentation, without a narrative, without confirming that no more specific code applies — it tends to generate denials, audit attention, and payer friction that outweigh the revenue.psychiatry+2
This guide covers when 90899 actually applies, how to build a claim that can survive review, and where providers most often go wrong.
What CPT 90899 Is
CPT 90899 sits at the end of the Psychiatry Services and Procedures code range (90785–90899) and carries the official descriptor:vsac.nlm.nih+2
Unlisted psychiatric service or procedure.
That language is intentionally broad. As with other “unlisted” codes in CPT, 90899 serves as a catch‑all for psychiatric services that are not specifically defined elsewhere in the psychiatry section — often because they are new, unusual, or too specialized to justify their own dedicated code yet.aapc+1
The psychiatry CPT code set covers a lot of ground: time‑based individual psychotherapy (90832, 90834, 90837), group psychotherapy (90853), psychiatric diagnostic evaluations (90791, 90792), psychotherapy with medication management (90833, 90836, 90838), crisis services (90839/90840), and specific procedural interventions like transcranial magnetic stimulation (90867–90869) and ECT (90870). When none of those — or any other specific psychiatry code — accurately describe what was done, 90899 is the correct fallback.aacap+3
What 90899 is not:
A “miscellaneous” code for services you’re unsure how to bill. CPT and CMS both emphasize that unlisted codes should only be used when no specific HCPCS/CPT code adequately describes the service.centralhealthplan+2
A workaround for plan exclusions. If a benefit is explicitly non‑covered, reporting it under an unlisted code does not change the underlying coverage determination.cms+1
An automatically payable code. Unlike codes with assigned relative value units (RVUs), 90899 has no standard national fee; payers price it case‑by‑case based on documentation and internal policy.optumcoding+2
When 90899 Actually Applies
Before you reach for 90899, you always ask one question: Does a more specific code exist that accurately describes this service? CPT, CMS, and payer policies all require that specific codes be used when available; unlisted codes are a last resort.centralhealthplan+1
Legitimate behavioral health use cases for 90899 tend to fall into a few buckets:
Emerging or non‑standard therapy formats where the type of service isn’t psychotherapy as defined in CPT
Most therapy modalities — EMDR, CBT, DBT, somatic approaches — are reported under standard psychotherapy time codes (90832/90834/90837) when delivered as individual psychotherapy sessions; the modality does not by itself justify 90899. In narrow cases, adjunctive or structured components that don’t fit psychotherapy, diagnostic evaluation, or testing definitions may justify unlisted reporting, but that’s the exception.aapc+1
Ketamine‑assisted or other medication‑adjacent psychotherapeutic work
The infusion or injection component of ketamine treatment is typically billed using infusion/injection codes (for example, 96365/96366 for IV services) when covered. The psychotherapeutic “processing” sessions around the infusion often fit standard psychotherapy codes. When a program is delivering structured, protocol‑driven work that does not map cleanly to existing psychotherapy, diagnostic, or HBAI codes, 90899 may be considered, but payers will scrutinize this closely and coverage varies.[cms]
Novel group formats that fall outside 90853
Standard, therapist‑led group psychotherapy is reported using 90853. If you are delivering a structured group that truly does not meet the CPT definition of group psychotherapy — for example, a hybrid model combining psychoeducation, family systems work, and protocolized behavioral drills that doesn’t match 90853 or any other existing code — 90899 can be used with detailed explanation.prc.hmsa+2
Psychedelic‑assisted therapy preparation and integration
As MDMA‑assisted and psilocybin‑assisted therapies move through regulatory pathways, coding guidance is still evolving. Some programs are using standard psychotherapy codes for preparation and integration sessions, while others have explored 90899 when their protocols differ significantly from defined psychotherapy or evaluation services. In all cases, the safest path is to match the service to an existing code wherever possible and reserve 90899 for clearly unlisted services.psychiatry+1
Specialized assessments without a direct match
Occasionally, structured clinical assessments or rating‑scale protocols used in complex cases do not neatly align with 90791/90792 (diagnostic evaluations), 96130+ (psychological testing), or other existing codes. When a service is demonstrably distinct from those categories and not captured by testing or evaluation codes, 90899 is an option — but you should be prepared to explain that distinction in writing.cms+1
Truly experimental or research‑linked interventions
When you’re delivering novel neuromodulation, unique combined protocols, or other emerging treatments that lack specific coding — and are not clearly covered under existing codes — 90899 may be the only code available for reporting. In these situations, coverage is highly variable, and many payers may classify the service as investigational.upvio+2
The throughline: 90899 is for services that genuinely do not fit any defined psychiatry code; it is not a code of convenience.
The Prior Authorization Problem — and How to Handle It
Because unlisted codes don’t have built‑in RVUs or tightly defined coverage rules, payers handle them differently from standard codes. CMS guidance on unlisted codes notes that contractors should only pay them when they’ve verified that no more specific code applies and that the service is reasonable and necessary, with payment determined by comparison to analogous covered services.prc.hmsa+1
In practice, that means more up‑front work.
Before Delivering the Service
1. Verify coverage with the payer.
For any service you intend to bill under 90899, call provider services and ask:
Whether the plan covers unlisted psychiatric services under 90899.
Whether prior authorization is required for 90899 in general or for this specific service category.
Document the call: date, representative name, call reference number, and exactly what you were told.centralhealthplan+2
2. Request prior authorization when possible.
Even when not explicitly required, submitting a PA request with:
A clear description of the proposed service.
A comparison to the closest CPT code (for example, psychotherapy or TMS) and an explanation of why it doesn’t fit.
A medical necessity letter summarizing diagnosis, prior treatment history, rationale, and evidence base.
gives the payer a structured foundation for later payment decisions.optumcoding+2
3. Establish a comparison code and a target rate.
Payers often price 90899 by analogy to the most similar code in terms of time, complexity, and clinical work. If your service is most like a 60‑minute psychotherapy session (90837) or a TMS session (90868), say that explicitly in your PA request and later in your claim narrative and set your billed amount accordingly.cms+1
Building the Documentation Package
Because 90899 has no fixed descriptor beyond “unlisted psychiatric service,” payers rely heavily on the accompanying documentation.
The Cover Letter / Narrative
Many payer and coding resources recommend including a descriptive narrative when reporting unlisted codes like 90899; some explicitly direct providers to add this to the claim or a cover attachment. Your narrative should include:psychiatry+3
Service description: What exactly was done, in clinical terms, including setting, duration, and participants.
Why 90899 is needed: A statement that no specific CPT code accurately describes the service and why commonly considered alternatives (e.g., 90837, 90853, 90791) are not accurate.aapc+2
Comparison code: The closest CPT code, similarities and differences, and why you chose that as the pricing anchor.
Billed amount rationale: How you derived your charge (for example, “comparable in time and complexity to 90837 plus X additional components”).
A 90899 claim submitted with only a generic claim line and no narrative leaves payers little basis for anything but a denial or request for more information.
The Clinical Note
The supporting clinical documentation should read like something you’d send with a prior authorization or appeal. It should clearly show:optumcoding+2
The patient’s diagnosis, history, and current presentation.
The specific intervention or service delivered, not just the modality label.
Time spent and, where relevant, intensity/complexity (even though 90899 itself isn’t strictly time‑tiered).
The clinical rationale for choosing this service over standard interventions.
The patient’s response and how this ties into the treatment plan.
For innovative or emerging treatments, referencing peer‑reviewed literature or guidelines in your narrative can strengthen the case for medical necessity.
ICD-10 Code Selection
90899 can be paired with any behavioral health diagnosis as long as the service is clearly aimed at that condition and medically necessary. Use the most specific code available — for example, F33.2 (major depressive disorder, recurrent, severe) instead of a generic depressive episode code — when severity or treatment resistance is part of your rationale. The diagnosis alone won’t secure coverage, but it frames the clinical picture.mthf+1
Reimbursement Reality
There is no national Medicare fee schedule value assigned to 90899 in the way there is for standard psychiatry codes. Payment is contractor‑ and payer‑specific.payerprice+2
Medicare: APA’s coding resources note that 90899 is intended for services not defined under other codes and that Medicare generally requires a descriptive narrative and may not routinely reimburse certain uses (for example, report‑only services without face‑to‑face care). MACs determine coverage and pricing case‑by‑case, often by analogy to the nearest covered service.cms+1
Commercial payers: Some plans will pay 90899 at a rate similar to your comparison code when documentation is strong; others default to denial or require appeals with additional records. Coverage for specific emerging interventions (e.g., ketamine‑assisted psychotherapy) is highly variable across plans.payerprice+2
Medicaid: State Medicaid programs often have narrow behavioral health coverage policies and may treat many unlisted/experimental services as non‑covered, even if billed under 90899. Reviewing state manuals and Medicaid contractor policies before using 90899 is critical.[mthf]
For out‑of‑network or self‑pay practices, listing 90899 on a superbill allows patients to attempt out‑of‑network reimbursement, but you should be explicit that reimbursement is not guaranteed and the patient is financially responsible regardless of the payer’s decision.trytwofold+1
Static reimbursement ranges published in secondary sources should be treated as illustrative only; the actual allowed amount depends on each payer’s internal pricing and your contracts.trytwofold+1
The “Should I Use 90899 or a Specific Code?” Decision Framework
A quick decision tree that matches CPT and CMS guidance on unlisted codes:aapc+3
Is this individual psychotherapy (regardless of modality)?
Use 90832/90834/90837 based on time. EMDR, CBT, ACT, and similar modalities are all billed under standard psychotherapy codes when delivered as therapy sessions.Is this group psychotherapy?
Use 90853 if it meets the definition (therapist‑led, interactive group psychotherapy).Is this a diagnostic evaluation?
Use 90791 or 90792 depending on whether medical services are provided.Is this crisis psychotherapy?
Use 90839/90840 when criteria for crisis are met.Is this TMS or ECT?
Use 90867–90869 for TMS, 90870 for ECT.aacap+1Does another specific psychiatric, HBAI, or testing code accurately describe this service?
If yes, use that code.If no specific code fits and the service is medically necessary
And you have a clear description, rationale, and comparison code, 90899 is appropriate.
If you find yourself using 90899 frequently for services that peers routinely bill with standard codes, that’s a sign to revisit your coding rather than a strategy to embrace.
Common Compliance Risks
Patterns that appear across payer and coding guidance include:prc.hmsa+4
Using 90899 when a specific code exists
Reporting 90899 for routine psychotherapy, group therapy, or diagnostic work that clearly falls under an existing code is the most basic misuse and can be characterized as incorrect coding or upcoding.
Submitting 90899 without a descriptive narrative
Resources from APA and large payers emphasize that unlisted codes must be accompanied by a descriptive narrative of the service. Without it, many claims are denied or returned for additional information.psychiatry+3
No comparison code or pricing rationale
Payers need a benchmark for payment. Failing to identify the most analogous code and explain your charge leaves them guessing — and they may default to the lowest plausible payment or deny outright.centralhealthplan+1
Improper stacking with other services
CMS and commercial NCCI edits restrict certain combinations of psychiatric codes on the same day; billing 90899 along with codes that already describe the same time and service (for example, a time‑equivalent psychotherapy code) can trigger bundling edits and audits.cms+1
Weak medical necessity documentation
If the record doesn’t clearly explain why a non‑standard or unlisted service was indicated — especially when prior standard treatments exist — payers are more likely to classify it as experimental or not medically necessary.psychiatry+1
Patient financial transparency gaps
For interventions that may be investigational or not widely covered, documenting that the patient was informed about coverage uncertainty and financial responsibility is a key risk‑management step.upvio+1
FAQ: CPT Code 90899
Can 90899 be billed for EMDR sessions?
In most situations, EMDR sessions are billed under the standard psychotherapy codes (90832/90834/90837) based on time, because EMDR is a modality of psychotherapy rather than a distinct service type in CPT. 90899 would only be appropriate if you are delivering a service that truly falls outside psychotherapy definitions and cannot be reported with psychotherapy, evaluation, or testing codes.aapc+1
Does Medicare cover 90899?
Medicare does not publish a fixed fee schedule rate for 90899, and APA materials note that Medicare typically requires detailed justification when unlisted psychiatric codes are used. Coverage is determined case‑by‑case by the Medicare Administrative Contractor, often based on whether the service can be analogized to a covered service and is reasonable and necessary.cms+2
How should I set my charge for 90899?
A common approach is to base your charge on the most analogous existing code’s usual charge, adjusted for time and complexity, and then explain that rationale in your narrative. Charging far above comparable codes without explanation increases the likelihood of adjustments or denials.centralhealthplan+1
Can 90899 be used for telehealth?
CPT does not prohibit reporting 90899 via telehealth when the underlying service is appropriately delivered remotely, but coverage is payer‑specific. If you use 90899 for telehealth, document the modality, use the correct telehealth place‑of‑service and modifiers, and verify payer telehealth policies in advance.ama-assn+1
What if a payer denies a 90899 claim?
If the denial is for missing detail, you can often appeal with a fuller narrative and supporting clinical notes; if the denial is based on non‑coverage or the existence of a more appropriate code, your options are more limited and may involve benefit review or parity arguments when appropriate.cms+2
Is prior authorization always required for 90899?
Not universally, but many commercial plans flag unlisted codes for prior review, and several payer policies explicitly require documentation and medical review for unlisted psychiatric services. Checking and, when in doubt, proactively submitting a PA request is often the safer path.prc.hmsa+2
Building a Sustainable Process Around 90899
90899 is inherently a high‑touch code. Without a process, every claim becomes an improvisation. Practices that routinely bill 90899 — for emerging modalities like ketamine‑assisted therapy, psychedelic‑adjacent services, or structured novel groups — do best when they standardize:
A cover‑letter template for each service type.
A payer verification and PA checklist.
Clinical note templates that meet unlisted‑code documentation expectations.
A billing/UR team (in‑house or external) that understands unlisted‑code pricing, appeals, and payer patterns.optumcoding+2
Those are the programs most likely to consistently obtain reimbursement for innovative services without creating unnecessary audit risk.
ForwardCare is a behavioral health MSO that partners with clinicians, program operators, and healthcare entrepreneurs to build and scale addiction and behavioral health treatment programs — including the billing infrastructure needed to handle complex and emerging code scenarios like 90899. If you’re building a program and want operations designed to support both standard and innovative services, ForwardCare is worth a conversation.
