Resources

Medical billing terms explained

Short definitions with a worked example and an annotated sample for each, written by the billers who build Iridium Suite. New terms are added every week.

0-9

77387 Modifier 26 in Medical Billing: How Image Guidance Is Reported in 2026: 77387 modifier 26 is the only separately billable piece of image guidance in 2026. Why the technical component is bundled, how often to report it, what freestanding centers lost, and the first-year rejections.
77407 vs 77412 in Medical Billing: Choosing the Radiation Treatment Delivery Level in 2026: 77407 vs 77412 is the Level 2 versus Level 3 decision for every 2026 radiation treatment fraction. The exact criteria, the single-isocenter rule, what the record must show, and why payers downgrade.

A

Allowed Amount in Medical Billing: Billed vs Allowed vs Paid, and the CO-45 Write-Off: The allowed amount is the most a payer will recognize for a service; the gap to your charge is the CO-45 contractual adjustment. Billed vs allowed vs paid, participating vs non-participating, and the limiting charge.
ASP Plus 6 Percent: How Medicare Part B Pays for Drugs, and What Is Left After Sequestration: ASP plus 6 percent is Medicare's payment limit for most Part B drugs: average sales price two quarters back plus 6 percent, set quarterly. Sequestration, the inflation rebate, 340B, biosimilars and 2028 negotiation.

B

Brachytherapy CPT Codes in Medical Billing: Code Families, Once-Per-Course Items and Site of Service: Brachytherapy CPT codes by family: intracavitary 77761 to 77763, HDR 77770 to 77772 by channel count, interstitial 77778, isodose plans 77316 to 77318, plus what is bundled and how hospital billing differs.

C

CHAMPVA Cards and Billing: How to Read the Card and File the Claim: CHAMPVA is the VA health benefit for spouses and children of permanently disabled or deceased veterans. What the card shows, how it differs from TRICARE, and how a practice files and gets paid.
Chemotherapy Administration Codes 96413, 96415 and 96417: Initial, Sequential, Concurrent and the Infusion Hierarchy: Chemotherapy administration codes 96413, 96415 and 96417 and the infusion hierarchy: one initial service per encounter, the 16 and 31 minute thresholds, push versus infusion, and a worked infusion day.
Claim Denial Rate in Medical Billing: Initial vs Final, How to Count It, and Benchmarks: Claim denial rate is the share of claims a payer denies on first submission. Initial denials versus final write-offs, counting by claim, line or dollars, MGMA and AAFP benchmarks, and the top CARC causes.
Clean Claim Rate in Medical Billing: Definition, How to Measure It, and the Target: Clean claim rate is the share of claims the payer accepts and adjudicates on first submission with no rejection or error denial. How to measure it from the 277CA and 835, the usual target, and what moves it.
CMS-1500 Form Box by Box: What Each Field Means and Which Ones Cause Denials: The CMS-1500 form (version 02/12) is the standard paper claim for physicians and suppliers, and the 837P is its electronic version. Every box, grouped by what it does, and the ones that get claims denied.
Coordination of Benefits in Medical Billing: Primary vs Secondary, the Birthday Rule and MSP: Coordination of benefits is how payers decide who pays first when a patient has more than one plan. The birthday rule, Medicare Secondary Payer basics, the MSP questionnaire and CO-22 denials explained.
CPT 77263 in Medical Billing: Simple, Intermediate and Complex Treatment Planning, and the Z51.0 Diagnosis: CPT 77263 is complex radiation treatment planning, reported once per course. What separates it from 77261 and 77262, when Z51.0 is the first-listed diagnosis and when it is not, and what the note must contain.
CPT 77290 in Medical Billing: Simple, Intermediate and Complex Simulation, Plus the 77293 Add-On: CPT 77290 is complex radiation therapy simulation. What separates it from 77280 and 77285, when the 77293 respiratory motion add-on applies, why none of them bill during IMRT, and the same-day image guidance rule.
CPT 77301 in Medical Billing: IMRT Planning in 2026 and the Codes Around It: CPT 77301 is IMRT planning, reported once per course. What the plan includes, how it relates to 77338, 77300, 77370 and 77295, what changed when 77014, 77385 and 77386 were deleted, and payer criteria.
CPT 77334 in Medical Billing: Simple, Intermediate and Complex Treatment Devices, and 77338 for IMRT: CPT 77334 is a complex radiation treatment device such as a custom mold, compensator or irregular block. How it differs from 77332 and 77333, when 77338 applies to IMRT, units per course, and modifiers 59 and XE.
CPT 77336 in Medical Billing: Continuing Medical Physics Consultation, Per Five Fractions: CPT 77336 is continuing medical physics consultation, one unit per five fractions alongside 77427; 77370 is the special physics consultation, once per course. Who performs and bills them, and where the counts diverge.
CPT 77427 in Medical Billing: Radiation Treatment Management, Five Fractions at a Time: CPT 77427 is radiation treatment management, billed once per five fractions. How the count works, the three-or-four rule at the end of a course, what to document, and how it differs from 77431, 77432 and 77435.
CPT 77470 in Medical Billing: The Special Treatment Procedure, Once Per Course: CPT 77470, the special treatment procedure, is one unit per course when a radiation course needs extra physician and staff work: concurrent chemotherapy, pediatric sedation, re-irradiation. What to document.

D

Days in A/R in Medical Billing: Formula, What Is Good, and a Worked Example: Days in A/R is total accounts receivable divided by average daily charges: how many days of billing sit unpaid. The MGMA and HFMA versions, what counts as good, why oncology runs higher, and a worked example.

E

EDI in Medical Billing: The 837, the 835 and the Other HIPAA Transactions Explained: EDI in medical billing is the set of HIPAA X12 transactions that carry claims (837), remittances (835), eligibility (270/271) and claim status (276/277) between practice, clearinghouse and payer. How one claim travels.
ERA in Medical Billing: EOB vs ERA vs Remittance Advice, and Who Receives Which: An ERA in medical billing is the electronic remittance advice (the X12 835) a payer sends the provider; the EOB is the version the patient receives. What each is for, and how posting differs.

F

Facility vs Non-Facility Rates in Medical Billing: Why the Office Price Is Higher: Facility vs non-facility is the two-price structure of the Medicare physician fee schedule. The non-facility rate pays the practice for its room, staff and equipment; the facility rate assumes a hospital bills for them.
First Pass Resolution Rate in Medical Billing: Definition, Formula, and How It Relates to Denials: First pass resolution rate is the share of claims paid on first submission with no rejection, correction or appeal. How it differs from clean claim rate and denial rate, and how to compute it from your billing system.

G

Global Charges in Medical Billing: Knowing the Difference Between Global, Professional and Technical Charges: Global charges in medical billing cover a whole service; professional and technical charges split it between the physician and whoever owns the equipment. How to tell which one your practice bills, and why.
GRP/RC-AMT on a Medicare Remittance: Group Codes, Reason Codes and Amounts Explained: GRP/RC-AMT on a Medicare remittance shows the group code, reason code and dollar amount for every adjustment a payer made to a service line, such as CO-45 338.24. Here is how to read each part, with a worked example.

H

HIC Number, MBI and ICN: The Three Medicare Numbers Billers Mix Up: The HIC number was Medicare's Social Security-based patient ID, replaced by the 11-character MBI between 2018 and 2020. The ICN is the claim number on the remittance. What each looks like and which to use when.
Hyperfractionation Billing: How to Bill Twice-Daily (BID) Radiation Fractions: Hyperfractionation billing means two fractions on one date: bill each delivery, the second with modifier 76, count 77427 and 77336 by fractions rather than days, and add the BID note payers expect.

I

Incident-to Billing: What Does Incident To Mean in Medicare Billing?: Incident to billing lets a physician bill office services that staff or an NPP furnish under direct supervision, at the full physician rate. Medicare's requirements, the 2026 supervision change, oncology examples.

J

J-Codes Medical Billing Rules: Units, NDC Reporting and the Unlisted Drug Codes: J-codes medical billing rules in one place: the HCPCS unit versus the dose, the 11-digit NDC with the N4 qualifier in box 24 or loop 2410, who requires it, and how to bill J3490, J9999 and C9399.
JW Modifier and JZ Modifier in Medical Billing: Discarded Drug Billing from Single-Dose Vials: The JW modifier bills the amount discarded from a single-dose vial on its own line; JZ attests nothing was discarded. Medicare's dates, the exceptions, the manufacturer refund, and worked examples with units.

M

Medically Unlikely Edits (MUE) in Medical Billing: Unit Limits, MAI 1, 2 and 3, and What to Do: Medically unlikely edits are CMS unit-of-service limits per code, per patient, per day. How they differ from NCCI PTP edits, what MAI 1, 2 and 3 mean, and how to bill units above the limit when they are real.
Medicare Crossover Claims: How Medicare Forwards to Medigap and Medicaid, and When to Bill the Secondary Yourself: Medicare crossover claims are claims Medicare forwards to the patient's Medigap, Medicaid or other secondary payer after it pays. How COBA works, what MA18 and MA07 mean, and when to bill the secondary yourself.
Medicare Secondary Payer ESRD Rules: The 30-Month Coordination Period and How to Bill It: Under the Medicare Secondary Payer ESRD rule a group health plan pays first for 30 months of Medicare eligibility. How to count the months, ask the MSP questions, and bill the plan, then Medicare.
Medicare Sequestration: The 2 Percent Payment Reduction, CO-253 and the Arithmetic: Medicare sequestration is the 2 percent cut taken from Medicare's share of each fee-for-service payment, shown on the remittance as CO-253. How it is calculated, its history, and why the patient never pays it.
Modifier 26 and Modifier TC in Medical Billing: Professional, Technical and Global Components: Modifier 26 bills the physician's professional component of a split code and TC bills the equipment and staff. Which codes split, who bills which by site of service, and the denials to expect.
Modifier Q6 and Locum Tenens Billing: Fee-for-Time Arrangements, the 60-Day Rule and Which NPI to Use: Modifier Q6 tells Medicare a substitute physician furnished the service under a fee-for-time (formerly locum tenens) arrangement, billed under the regular physician's NPI. The 60-day rule, Q5, and the record to keep.

N

Net Collection Rate in Medical Billing: Formula, Gross vs Net, and a Worked Example: Net collection rate is payments divided by charges minus contractual adjustments: the share of collectible money actually collected. Gross versus net, the 90 to 120 day lag, what a low rate means, and a worked example.
NPI Numbers in Medical Billing: Type 1 vs Type 2, and Rendering vs Billing Provider: An NPI is the 10-digit National Provider Identifier on every claim. Individuals hold a Type 1, organizations a Type 2, and the rendering and billing boxes often need different ones. Which goes where.

P

Place of Service 22 (On Campus Outpatient Hospital): What It Means and How It Changes Payment: Place of service 22 means an on-campus outpatient hospital department. The hospital owns the room and equipment, so the physician is paid the facility rate and bills the professional component only.
Place of Service Codes in Medical Billing: The Full List and the Ones Billers Mix Up: Place of service codes are the two-digit codes in box 24B that tell a payer where a service happened. The full CMS list, the codes billers confuse (02, 10, 11, 19, 22) and how POS sets the facility or non-facility rate.
PR 1 in Medical Billing: PR-1 Deductible, PR-2 Coinsurance and PR-3 Copay Explained: PR 1 in medical billing is the deductible, PR-2 the coinsurance and PR-3 the copay: what a remittance says the patient owes. How to post them, bill the secondary, and spot a PR that should have been CO.
Proton Therapy CPT Codes in Medical Billing: 77520 to 77525, Contractor Pricing and the APCs: The proton therapy CPT codes 77520 to 77525 are priced by each MAC under the fee schedule and paid through APCs 5623 and 5625 in the hospital. How the two systems differ, where coverage comes from, and the 2027 proposal.
PTAN Number in Medical Billing: What It Is, How It Differs From the NPI, and Where You Use It: A PTAN number is the Provider Transaction Access Number a Medicare contractor assigns when it approves your enrollment. It is not the NPI and never goes on a claim; you use it with the MAC's portal, IVR and EDI setup.

R

Radiation Oncology Modifiers in Medical Billing: The 2026 Cheat Sheet for 26, TC, 59, 76, Q6, KX and the Rest: Radiation oncology modifiers in one table: which codes split into 26 and TC, when 59 or an X modifier is allowed, 76 for a second same-day fraction, Q6, KX, GC, telehealth 77427, JW and JZ, and what no longer matters.
Remark Codes in Medical Billing: RARC vs CARC, and What MA01, MA18, N290 and N807 Mean: Remark codes (RARCs) are the MA, M and N codes on a remittance that explain an adjustment or give information a reason code cannot. How they differ from CARCs, where they appear, and what the common ones mean.
Rendering Provider vs Billing Provider: Who Goes in Which Box on the Claim: The rendering provider performed the service; the billing provider gets paid for it. How the referring, supervising and pay-to roles fit, and where each one goes on the CMS-1500 and the 837P.

S

SBRT Billing Codes in Medical Billing: 77373, 77435 and the Five-Fraction Course: SBRT billing codes are 77373 per delivered fraction and 77435 for managing the whole course, never more than five fractions. How they pair with cranial SRS, planning codes and hospital billing in 2026.
Superficial Radiation Therapy CPT Codes in Medical Billing: 77436 to 77439 and the End of 77401: The superficial radiation therapy CPT codes 77436 to 77439 replaced 77401 and G6001 in 2026. What each covers, the kV cutoffs, the once-per-course ultrasound add-on, the Medicare KX modifier and where payers disagree.

T

Taxonomy Code in Medical Billing: The 10-Character Specialty Code and When It Goes on the Claim: A taxonomy code is the 10-character NUCC specialty code attached to every NPI in NPPES. Where it goes on the CMS-1500 and 837P, which payers ask for it, and the codes oncology practices use most.
The ESRD Monthly Capitation Payment in Medical Billing: 90951 to 90970: The ESRD monthly capitation payment is one Medicare payment a month for managing a dialysis patient. The age bands, the 1, 2 to 3 and 4 or more visit tiers, home dialysis and per-day codes, and the one-physician rule.
The Global Surgical Package in Medical Billing: 0, 10 and 90 Day Global Periods: The global surgical package is one Medicare payment for a surgery and its routine care before and after. The 000, 010, 090, XXX, YYY and ZZZ indicators, modifiers 24, 25, 57, 58, 78 and 79, and urology examples.
Timely Filing Limit in Medical Billing: Medicare's 12 Months, Payer Windows and CO-29: A timely filing limit is the deadline for a payer to receive a claim, counted from the date of service. Medicare allows 12 months; commercial and Medicaid windows vary. How to prove filing and handle CO-29.
TRICARE Billing for Providers: Regions, Contractors, Network Status and TRICARE For Life: TRICARE billing follows the patient's region: Humana Military in the East, TriWest in the West, WPS for TRICARE For Life. Who is covered, network versus non-network, and how it differs from CHAMPVA and VA care.

U

Understanding an EOB (Explanation of Benefits): What It Means, What It Shows and What to Do With It: An EOB, or explanation of benefits, is the statement a health plan sends after processing a claim: what was billed, what the plan allowed and paid, and what the patient may owe. It is not a bill.
Urology Billing for In-Office Procedures: Cystoscopy, Urodynamics, Catheter Changes and Injections: Urology billing for the procedure room: the 52000 cystoscopy family, urodynamics 51725 to 51798, catheter codes 51702 and 51703, instillation 51720 with its drug line, in-office labs under CLIA, and modifier 25.