Direct answer: Medical billing and insurance terms describe the people, codes, documents, transactions, payments, and rules involved in processing healthcare claims. Understanding terms such as CPT, ICD-10-CM, HCPCS, NPI, EOB, ERA, deductible, coinsurance, denial, and prior authorization helps providers and patients communicate more clearly about billing.
Last reviewed: August 2026. Definitions may vary by payer, contract, program, and care setting. This glossary provides general information and is not legal, coding, or payer-specific advice.
Quick Medical Billing Abbreviation Guide
| Abbreviation | Meaning |
|---|---|
| A/R | Accounts receivable |
| ABN | Advance Beneficiary Notice of Noncoverage |
| BAA | Business associate agreement |
| CARC | Claim Adjustment Reason Code |
| COB | Coordination of benefits |
| CPT | Current Procedural Terminology |
| EFT | Electronic funds transfer |
| EOB | Explanation of benefits |
| ERA | Electronic remittance advice |
| HCPCS | Healthcare Common Procedure Coding System |
| HIPAA | Health Insurance Portability and Accountability Act |
| ICD-10-CM | International Classification of Diseases, Tenth Revision, Clinical Modification |
| MAC | Medicare Administrative Contractor |
| NCCI | National Correct Coding Initiative |
| NPI | National Provider Identifier |
| PHI | Protected health information |
| POS | Place of service |
| RARC | Remittance Advice Remark Code |
Health Insurance and Patient-Cost Terms
Allowed Amount
The maximum amount a health plan recognizes for a covered service under its payment rules or provider contract. It may also be called the negotiated rate, eligible expense, or payment allowance.
The allowed amount can differ from the provider’s full charge. Patient responsibility is generally calculated from the applicable allowed amount, benefits, network status, and plan rules.
Benefit
A healthcare service or item covered under the terms of a health plan. Coverage may still depend on medical necessity, network requirements, authorization, patient eligibility, exclusions, and other conditions.
Coinsurance
The percentage of an allowed amount that a patient may owe for a covered service, often after satisfying the applicable deductible.
Copayment
A fixed amount a patient may owe for a covered service. Copayments can differ by service type, provider, care setting, and plan.
Coordination of Benefits
The process used to determine the payment order when a patient has coverage from more than one health plan. It identifies which plan is primary, secondary, or otherwise responsible.
Covered Service
A service or item included under a health plan’s benefits when applicable requirements are satisfied. A covered service is not necessarily paid in full.
Deductible
The amount a patient generally pays for certain covered services before the health plan begins paying under the plan’s rules. Some services may be covered before the deductible is met.
Exclusion
A service, item, condition, or circumstance that the health plan does not cover under its terms.
In-Network Provider
A provider or facility participating in a health plan’s network under an applicable contract. Participation can vary by plan, location, provider, and effective date.
Out-of-Network Provider
A provider or facility that does not participate in the patient’s specific plan network. Patient costs and coverage may differ, and federal or state patient-protection rules may apply in certain situations.
Out-of-Pocket Costs
Healthcare expenses paid by the patient rather than reimbursed by insurance. Depending on the plan, these can include deductibles, copayments, coinsurance, and costs for noncovered services.
Out-of-Pocket Maximum
The maximum amount a patient is generally required to pay for covered, qualifying services during a plan year. Premiums, noncovered services, and some out-of-network expenses may not count toward the limit.
Payer
An organization or program responsible for processing and paying eligible healthcare claims. Examples include commercial insurers, Medicare, Medicaid programs, and other health plans.
Premium
The amount paid for health insurance coverage, usually on a monthly basis, whether or not healthcare services are used.
Prior Authorization
A payer process requiring approval or review before certain services, procedures, medications, or equipment are provided. Authorization is not necessarily a guarantee of payment.
Referral
A direction or authorization from one healthcare professional for a patient to receive care from another provider. Some health plans require referrals for certain specialty services.
Subscriber
The person whose employment, enrollment, or relationship establishes the insurance coverage. The patient may be the subscriber or a covered dependent.
Medical Coding Terms
CPT
Current Procedural Terminology is a coding system maintained by the American Medical Association. It is primarily used to identify medical services and procedures performed by physicians and other healthcare professionals.
HCPCS
The Healthcare Common Procedure Coding System contains two primary levels:
- Level I: The CPT code set maintained by the American Medical Association.
- Level II: An alphanumeric code set maintained by CMS that identifies items and services such as supplies, drugs, ambulance services, and durable medical equipment not represented by CPT alone.
ICD-10-CM
A diagnosis classification system used across healthcare settings in the United States. It reports diseases, injuries, symptoms, conditions, and other reasons for healthcare encounters.
ICD-10-PCS
A procedure classification system used for reporting applicable procedures performed during inpatient hospital stays. It is different from ICD-10-CM diagnosis coding.
Diagnosis Code
A code identifying the patient’s condition, symptom, injury, or reason for care. Diagnosis codes help support coverage and medical-necessity review but do not independently guarantee payment.
Procedure Code
A code identifying a medical service, procedure, supply, drug, or item reported on a claim.
Modifier
A two-character addition to a CPT or HCPCS code that communicates a qualifying circumstance without changing the basic identity of the service.
Modifiers may identify a professional or technical component, distinct service, laterality, repeat procedure, bilateral service, or global-surgery circumstance. The documentation and payer rules must support their use.
NCCI
The National Correct Coding Initiative is a CMS program containing coding policies and edits intended to promote correct coding and reduce improper payments.
Procedure-to-Procedure Edit
An NCCI edit identifying code combinations that generally should not be reported together unless limited, supported circumstances allow separate reporting.
Medically Unlikely Edit
An NCCI edit addressing units of service reported for a code by the same provider or supplier for the same patient on the same date of service.
Place of Service
A two-digit code used on professional claims to identify the setting where the patient received the service. The place of service can affect coverage and payment.
Revenue Code
A code used on institutional claims to categorize the facility department, accommodation, supply, or service associated with a charge.
Medical Necessity
A coverage concept used to evaluate whether a service meets applicable clinical and payer requirements. Medical necessity policies vary by payer, benefit plan, program, and service.
Provider and Enrollment Terms
NPI
The National Provider Identifier is a unique 10-digit identifier assigned to covered healthcare providers and certain organizations for use in standard healthcare transactions.
Billing Provider
The individual or organization identified as the entity submitting and receiving payment for the claim, subject to enrollment and payer requirements.
Rendering Provider
The individual healthcare professional who performed or delivered the reported service.
Referring Provider
The provider who directs a patient to another professional or service. Payers may require the referring provider’s information for particular claims.
Ordering Provider
The healthcare professional who orders an item or service, such as a laboratory test, imaging study, home health service, or medical equipment.
Credentialing
The process of reviewing a provider’s qualifications, licenses, education, training, work history, and other professional information.
Payer Enrollment
The process of registering a provider or organization with a payer so that it may bill or participate under applicable program and contract requirements.
Taxonomy Code
A 10-character code identifying a healthcare provider’s classification and specialization. It is used in NPI and payer-enrollment records.
PECOS
The Provider Enrollment, Chain, and Ownership System is used for Medicare provider and supplier enrollment activities.
MAC
A Medicare Administrative Contractor is a regional organization that processes Medicare fee-for-service claims and performs other Medicare administrative functions.
Claim Forms and Electronic Transactions
CMS-1500
The standard paper claim form used by eligible non-institutional providers and suppliers for professional claims when paper submission is permitted.
CMS-1450 or UB-04
The standard paper claim form used by institutional providers such as hospitals and other eligible facilities.
837P
The standard electronic transaction used to submit professional healthcare claims.
837I
The standard electronic transaction used to submit institutional healthcare claims.
835
The standard electronic healthcare payment and remittance-advice transaction. It communicates payment, adjustment, denial, and patient-responsibility information.
Clearinghouse
An organization that receives healthcare transactions, checks or converts data, and routes transactions between providers and payers. Clearinghouse acceptance does not necessarily mean the payer accepted or paid the claim.
EDI
Electronic Data Interchange is the electronic exchange of standardized healthcare transactions, including claims, eligibility requests, claim-status inquiries, and remittance advice.
EFT
Electronic funds transfer is the electronic deposit of payer funds into a provider’s financial account.
ERA
Electronic remittance advice is the electronic explanation of how a payer processed a provider’s claim. It may include paid amounts, adjustments, denials, and patient responsibility.
EOB
An explanation of benefits is a health-plan document explaining how a patient’s claim was processed, including charges, plan payments, adjustments, and estimated patient responsibility. An EOB is not itself a bill.
Claim Processing and Payment Terms
Adjudication
The payer’s process for reviewing a claim and determining coverage, payment, adjustment, patient responsibility, or denial.
Clean Claim
A claim containing sufficient information to be processed without additional investigation or development before payment determination. Requirements can vary by payer and claim type.
Claim Rejection
A claim that fails an initial data, formatting, or submission requirement and may not enter payer adjudication. The error generally must be corrected before resubmission.
Claim Denial
A claim or service line that has been processed but not paid as submitted. The remittance information should explain the reason and may identify correction, documentation, reconsideration, or appeal options.
Corrected Claim
A replacement or adjustment submission used to correct information on a previously processed claim. Payers may require a frequency code, original claim number, or other identifying information.
Duplicate Claim
A claim or service that appears to repeat a previously submitted claim. Verify claim status before resubmitting an unpaid claim.
Timely Filing
The deadline by which a payer must receive an original claim, corrected claim, reconsideration, or appeal. Timeframes vary by payer and process.
Appeal
A formal request asking a payer to review an adverse claim or coverage decision. Appeals normally have documentation, submission, and deadline requirements.
Reconsideration
A payer review process that may be available for certain payment or claim decisions. Its meaning and requirements can differ by payer.
Remittance Advice
A provider-facing document or electronic transaction explaining how claims were processed and why payments differ from billed charges.
CARC
A Claim Adjustment Reason Code explains the general reason that a claim or service payment differs from the billed amount.
RARC
A Remittance Advice Remark Code supplies additional or more specific information about an adjustment or communicates an informational message.
Group Code
A remittance code that helps identify the general category of financial responsibility associated with an adjustment, such as patient responsibility or a contractual obligation.
Contractual Adjustment
The difference between a provider’s charge and the amount recognized under the applicable payer contract or payment arrangement. It should not automatically be transferred to the patient.
Patient Responsibility
The portion of an allowed charge assigned to the patient under the plan’s benefits and applicable billing rules. It can include a deductible, copayment, coinsurance, or noncovered amount.
Underpayment
A payment that may be lower than the amount required by the applicable contract, fee schedule, or payment policy. Not every difference between the charge and payment is an underpayment.
Overpayment
Funds received above the amount properly payable for a claim or service. Overpayments may require investigation, correction, refund, or payer notification.
Credit Balance
A balance showing that payments or adjustments exceed the amount currently owed on an account. It may belong to a payer, patient, or another party after review.
Revenue-Cycle Terms
Revenue Cycle Management
The financial and administrative process covering registration, eligibility, authorization, documentation, coding, charge entry, claim submission, adjudication, payment posting, denials, patient billing, and account resolution.
Accounts Receivable
Money owed to a provider for services already delivered and billed. A/R may include balances owed by payers and patients.
A/R Aging
A report grouping unpaid balances by the amount of time they have remained outstanding, often using ranges such as 0–30, 31–60, 61–90, and more than 90 days.
Days in A/R
A financial measure estimating how long it takes the organization to collect its accounts receivable. Calculation methods should remain consistent when comparing performance over time.
Charge Capture
The process of recording all reportable services, procedures, supplies, and other charges associated with patient care.
Claim Scrubbing
Reviewing a claim for missing, invalid, or inconsistent information before submission. Scrubbing can include demographic, provider, coding, authorization, and payer-specific edits.
Denial Management
The process of identifying, correcting, appealing, tracking, and preventing denied claims. Effective denial management addresses the original claim and the workflow that caused the denial.
Payment Posting
Recording payer and patient payments, adjustments, denials, and responsibility amounts in the billing system.
First-Pass Acceptance Rate
The percentage of claims accepted by the initial submission pathway without rejection. The definition should be documented because organizations may calculate it differently.
Privacy and Compliance Terms
HIPAA
The Health Insurance Portability and Accountability Act is a federal law associated with healthcare privacy, security, breach notification, and administrative simplification requirements.
PHI
Protected health information is individually identifiable health information held or transmitted by a covered entity or business associate in a protected context.
ePHI
Electronic protected health information is PHI created, received, maintained, or transmitted electronically.
Covered Entity
Under HIPAA, a covered entity may be a health plan, healthcare clearinghouse, or healthcare provider that conducts certain standard electronic transactions.
Business Associate
A person or organization performing certain functions or services for a covered entity that involve creating, receiving, maintaining, or transmitting PHI. Billing and claims-processing organizations can be business associates.
Business Associate Agreement
A written agreement establishing permitted PHI uses and disclosures and requiring appropriate safeguards and other HIPAA responsibilities between regulated parties.
Minimum Necessary
A HIPAA principle generally requiring reasonable efforts to limit certain PHI uses, disclosures, and requests to the information needed for the intended purpose. Exceptions and specific rules apply.
ABN
An Advance Beneficiary Notice of Noncoverage is a Medicare notice used in applicable circumstances before providing an item or service expected not to be covered. It is not a general waiver for every denied service.
Why Billing Terminology Matters
Misunderstanding one term can create incorrect claims, unnecessary patient confusion, missed appeal deadlines, inappropriate write-offs, or compliance problems.
Practices should use payer remittance information, current codebooks, contracts, official program guidance, and documented internal definitions rather than relying only on informal abbreviations.
When Medical Billing Support Can Help
A professional billing team can help interpret remittance information, maintain claim workflows, resolve denials, follow accounts receivable, and communicate billing issues clearly to providers and patients.
Learn more about our medical billing and coding services and accounts receivable support.
Frequently Asked Questions
What is the difference between an EOB and an ERA?
An EOB explains claim processing to the patient and is not a bill. An ERA communicates electronic claim payment and adjustment information to the provider.
What is the difference between a rejection and a denial?
A rejection generally fails an initial submission or data requirement before adjudication. A denial generally occurs after the payer processes the claim but does not pay it as submitted.
What is the difference between CPT and ICD-10-CM?
CPT primarily identifies professional services and procedures. ICD-10-CM identifies diagnoses, conditions, symptoms, injuries, and reasons for care.
Does having a procedure code mean the service is covered?
No. A code identifies a service or item but does not independently establish coverage, medical necessity, authorization, or payment.
Are copayments, deductibles, and coinsurance the same?
No. A copayment is generally a fixed amount, a deductible is an amount paid before certain plan benefits begin, and coinsurance is generally a percentage of an allowed amount.
