July 19, 2026
14 min read
By Albert Wong, PhD · Clinical Psychologist
The short answer
Insurance billing runs on about thirty terms. A claim is your request for payment, written in CPT codes (what you did) and ICD-10 codes (why). It travels through a clearinghouse as an 837 file, and the payer's answer comes back as an 835 — the ERA — while your client gets the human-readable EOB. Every dollar splits from the allowed amount, not from your fee. The rest of the language is defined below, one term at a time.
The first EOB arrives in your mailbox speaking a language nobody taught you. Allowed amount. Contractual adjustment. CO-45. It looks like a bill, except it says it isn't one, and somewhere in the fine print it has quietly decided how much of your fee exists. Your graduate program taught you to read a defended silence across the room. It did not teach you to read this.
Here's the thing about billing vocabulary: every term you don't know costs you something — money, sleep, or an hour on hold with a payer asking questions you could have answered yourself. So think of this glossary as a chart of the reef. The rocks don't move. Once you know where they are, you can sail past them for the rest of your career. If you want the story version — how a session becomes a deposit, start to finish — read our narrative walkthrough of the billing pipeline. This page is the chart. Bookmark it, and read your next EOB without flinching.
These are the words that describe the machinery — how a session leaves your office and comes back as money.
A claim is the formal request for payment a provider sends to an insurance company after delivering a service. For a therapist, one claim usually equals one session: it names the client, the date, the CPT code for what you did, the diagnosis code for why, the place-of-service code for where, and your fee. Nearly every other term in this glossary describes something that happens to a claim on its way to being paid.
A CPT (Current Procedural Terminology) code is a five-digit code, maintained by the American Medical Association, that tells the payer exactly what service you provided. A therapist's working set is small: 90791 for an intake, 90834 and 90837 for individual sessions of different lengths, 90847 for couples and family work, 90853 for group. Our guides to the CPT codes therapists actually use and choosing between 90837 and 90834 cover the details.
An ICD-10 code is the diagnosis code — the "why" that justifies the CPT code's "what." F41.1 is generalized anxiety disorder; F33.1 is recurrent major depression, moderate. Every claim needs at least one, and payers generally will not reimburse psychotherapy without a covered diagnosis, which is why "Z-codes only" claims (relationship distress, life transitions) are commonly denied.
A clearinghouse is the middleman between your EHR and the insurance company: it receives your claim, scrubs it for obvious errors, translates it into each payer's required format, and routes it to the right destination. Without one, you'd be uploading claims to dozens of payer portals by hand. Most modern EHRs, Practice Harbor included, have a clearinghouse built in.
An 837 is the standardized electronic file format a claim travels in — the envelope, not the letter. When your EHR says a claim was "submitted," it means an 837 file left for the clearinghouse. You will likely never open one, but knowing the name matters because payers and support reps use it constantly, as in "we never received the 837."
An 835, better known as an ERA (Electronic Remittance Advice), is the payer's electronic reply to your claim: what they allowed, what they paid, what the client owes, and any denial codes. Because it's machine-readable, an EHR can auto-post it — matching payments to sessions in seconds instead of the hour you'd spend typing them in from paper.
An EOB (Explanation of Benefits) is the human-readable version of the same information — the document the payer mails or posts explaining how a claim was processed. Crucially, an EOB is not a bill; it's the payer showing its math. When a client calls anxious about "a bill from insurance for $140," it's almost always an EOB showing the session went to their deductible.
A payer ID is the short code — usually five characters — that tells the clearinghouse which insurance company should receive a claim, like a routing number for claims. The same insurer can have different payer IDs for different plan types or states, which is why a claim for a Blue Cross client can bounce even though "Blue Cross" is obviously correct: the plan on their card routes to a different ID.
A taxonomy code is a ten-character code identifying your provider specialty — 1041C0700X for a clinical social worker, for example, or 103TC0700X for a clinical psychologist. It matters because some payers reimburse the same CPT code at different rates for different license types, and a mismatched taxonomy can hold up credentialing or claims.
An NPI (National Provider Identifier) is the free, permanent ten-digit number that identifies you to every payer in the country; you get it once from the federal NPPES registry and keep it for life. A Type 1 NPI identifies you as an individual clinician; a Type 2 NPI identifies a practice entity, which you'll want if you form a PLLC or hire associates.
The rendering provider is the clinician who actually delivered the session; the billing provider is the person or entity that gets paid. In a solo practice they're the same human, but the claim still asks for both — often your Type 1 NPI as rendering and your Type 2 as billing. In a group practice, the associate renders and the practice bills, and mixing those up is one of the most common causes of denied claims for new group owners.
Here's the part that decides what you actually earn. Every number on an EOB descends from one figure — the allowed amount — so start there and the rest falls into place.
The allowed amount is the maximum a payer will recognize for a service — the real price of the session, regardless of what you charge. If you bill $200 for a 90837 and the allowed amount is $120, every split that follows (deductible, coinsurance, payer payment) is calculated from $120; in-network, the remaining $80 is written off, not collected. This is the single most misunderstood number in therapy billing.
The contracted rate is the allowed amount you agreed to when you signed a payer's in-network contract — your negotiated price per CPT code. It's why two therapists across the hall can earn different amounts for identical sessions with the same insurer. Contracts can sometimes be renegotiated after a year or two of claims history, but only if you ask; payers do not volunteer raises.
A fee schedule is a price list by CPT code. Payers have one (their contracted rates for your license type), and your practice should have one too — the standard fees you charge everyone before any insurance adjustment. Your practice fee should sit above every contracted rate you hold, because payers will never pay more than you bill, even when their allowed amount is higher.
A deductible is the amount a client must pay out of pocket each plan year before insurance starts paying its share. A client with a $2,000 deductible who starts therapy in January will typically pay the full allowed amount — not your full fee — for their early sessions. This is why so many "covered" clients owe the whole cost of the session in the first months of the year.
A copay is a flat fee the client pays per visit — $25 per session, say — with insurance covering the rest of the allowed amount. It's the simplest client responsibility to collect: same number, every session, ideally charged the day of.
Coinsurance is a percentage split of the allowed amount between plan and client, usually after the deductible is met. On a $120 allowed amount with 20% coinsurance, the payer sends you $96 and the client owes $24. Unlike a copay, the client's share moves with the allowed amount, which is why their session cost can change when a payer updates its fee schedule.
The out-of-pocket maximum is the annual ceiling on what a client pays in deductibles, copays, and coinsurance combined; once they hit it, the plan pays 100% of covered services for the rest of the plan year. Weekly-therapy clients sometimes hit their max by fall — at which point their sessions become free to them, a fact worth checking before a client quits therapy over cost in October.
Courtesy billing is when an out-of-network therapist submits claims to the client's insurance on the client's behalf, as a service — the client typically still pays the therapist in full, and any reimbursement goes to the client. It's more work than handing over a superbill, less friction for the client, and requires no payer contract.
A superbill is a detailed receipt — your info, NPI, the client's diagnosis, CPT codes, dates, and fees paid — that an out-of-network client submits to their own insurance for reimbursement. The client pays you in full at the time of service; the superbill is how they claim their out-of-network benefits afterward. Every required field is covered in our superbill template guide.
Out-of-network benefits are the portion of a plan — typically a PPO — that reimburses care from providers who have no contract with the payer, commonly 50-80% of the plan's allowed amount after a separate, higher deductible. When a prospective client asks "do you take my insurance?" and you don't, the real question is whether their plan has out-of-network benefits — because if it does, a superbill may get them a meaningful chunk of your fee back.
Before the pipeline will carry your claims at all, you have to be let through the gate. These are the terms that govern who gets in, and on what conditions.
Credentialing is a payer's verification process — confirming your license, education, work history, malpractice coverage, and background — before it will let you join its network. It commonly takes 60 to 120 days per payer, and sessions you hold before your effective date are generally not payable, which is the classic new-practice cash-flow trap. The full process, payer by payer, is in our credentialing guide.
Paneling means being accepted onto a payer's network — its "panel" of in-network providers — with a signed contract and an effective date. Credentialing is the background check; paneling is the membership that follows. Panels can be closed: a payer with enough therapists in your zip code can simply decline to add you, no matter how clean your application is.
CAQH is a nonprofit that runs the shared online profile (CAQH ProView) most commercial payers use for credentialing — you maintain one master record of your license, history, and documents, and authorize payers to pull from it. The catch: you must re-attest that the profile is current roughly every 120 days, and a lapsed attestation can silently stall a credentialing application for weeks.
Prior authorization (or pre-auth) is a payer's requirement that you get approval before a service will be covered. In outpatient therapy it typically shows up around the edges — some plans require it after a set number of sessions, for extended sessions, or for psychological testing. Billing without a required auth earns a CO-197 denial, so verify the requirement when you check benefits, not after.
Medical necessity is the standard payers use to decide whether treatment is justified: a covered diagnosis, treatment aimed at that diagnosis, and documentation showing the two connect. In practice it means your notes should tie interventions to treatment-plan goals and goals to the diagnosis — "supportive conversation with a client who is doing well" is real therapy, but on paper it's a claim a payer can refuse.
Timely filing is the deadline for submitting a claim after the date of service — commonly 90 to 180 days for commercial payers; some allow a year, some Medicaid plans far less. Miss it and the claim is dead: the denial (CO-29) cannot be appealed on the merits, and you generally cannot bill the client for your own lateness. It is the only rock on this chart that sinks money permanently, which is why claims should go out weekly, not "when I get to them."
Coordination of benefits is the process that decides which plan pays first when a client has more than one — a child covered by both parents, or an adult with employer coverage plus a spouse's plan. The primary plan pays first and the secondary considers what's left. When a payer denies a claim "pending COB," it usually means the client needs to call and confirm which coverage is primary — a five-minute call that unfreezes every pending claim.
And they will, sometimes — not because you did anything wrong, but because the system leaks. The vocabulary of trouble is the most valuable part of the chart, because these are the terms you'll meet at the exact moment you're most stressed.
A rejection means the claim never made it into the payer's system — the clearinghouse or payer's front door bounced it for a formatting or data error, like a mistyped date of birth. A denial means the payer accepted and processed the claim, then refused to pay it. The difference matters: rejections are fixed and resubmitted as new claims, while denials require a corrected claim or a formal appeal.
The letters in front of an adjustment code on an ERA tell you who absorbs the money. CO (Contractual Obligation) means the provider does — the write-off between your fee and the allowed amount, or a denial you cannot bill the client for. PR (Patient Responsibility) means the client owes it — deductible (PR-1), coinsurance (PR-2), copay (PR-3). OA (Other Adjustment) is the miscellaneous bucket, common in COB situations. Read the letters before the numbers: they tell you whether you're writing off, billing the client, or fighting.
A clawback (formally, recoupment) is a payer taking back money it already paid you — usually after discovering the client's coverage had lapsed, another plan was primary, or an audit found a documentation problem. Payers typically recover it by shorting your future payments rather than asking for a check, which is why a mysteriously small deposit deserves a close reading of its ERA. Recoupment rights usually run back one to two years.
An appeal is the formal process for challenging a denial, with a letter and supporting documentation — the treatment plan, session notes, proof of authorization, whatever the denial reason demands. Deadlines are typically 30 to 180 days from the denial, and appeals succeed more often than demoralized therapists expect, because many denials are automated and fall over the moment a human reads the chart. Appeal within the week, every time.
An audit is a payer's review of your records against your claims — commonly triggered by statistical outliers, like billing nearly every session as 90837 when peers bill a mix. The payer requests charts for specific dates and checks that documentation supports what was billed: session start and stop times, medical necessity, a diagnosis that matches the claim. An audit is survivable if your notes were written for it all along.
That's the reef, charted. Thirty-odd terms, none of them difficult once named — and together they turn the EOB from a threat into a document you can skim in ninety seconds. The therapists who get paid reliably aren't fluent because they love billing; they're fluent because fluency is cheaper than confusion.
Practice Harbor generates the claims, talks to the clearinghouse, auto-posts your ERAs, and flags denials with their reason codes translated — so the glossary becomes trivia, not homework. Free for pre-licensed clinicians, $19/mo licensed.
An EOB (Explanation of Benefits) and an ERA (Electronic Remittance Advice) contain the same information — how a claim was processed, what the payer paid, and what the client owes — in two different forms. The EOB is the human-readable document sent to the client (and sometimes the provider), while the ERA is the machine-readable 835 file sent to the provider so an EHR can post payments automatically. Neither one is a bill.
The allowed amount is the maximum an insurance payer will recognize for a service, regardless of what the therapist charges. If a therapist bills $200 for a session and the allowed amount is $120, all payment math — deductible, copay, coinsurance, and the payer's share — is calculated from $120, and an in-network therapist writes off the remaining $80. For in-network providers, the allowed amount equals their contracted rate.
A rejection means the claim never entered the payer's processing system — it was bounced by the clearinghouse or payer front-end for a data or formatting error, and can simply be corrected and resubmitted. A denial means the payer processed the claim and refused to pay, citing a reason code on the ERA; fixing it requires a corrected claim or a formal appeal, usually within 30 to 180 days.
A clearinghouse is an intermediary between a provider's billing system and insurance payers. It receives claims as 837 files, scrubs them for errors, translates them into each payer's required format, and routes them to the correct payer — then routes the payer's 835/ERA response back. Most therapy EHRs include a built-in clearinghouse connection, so a solo therapist never has to submit claims to individual payer portals by hand.