CPT & HCPCS Modifiers

A category-organized, searchable reference to the most-billed CPT (Level I) and HCPCS Level II modifiers. Each modifier has its own page. Search a code (e.g., 25, 59, LT) or a keyword.

How modifiers work

A modifier is a two-character code appended to a CPT/HCPCS code that adds detail without changing its meaning. Pricing modifiers (50, 51, 52, 53, 62, 66, 80/81/82/AS, 26, TC, anesthesia AA/QK/QX/QY/QZ) change the allowed amount and must be sequenced before informational ones. CPT modifiers are numeric (AMA); HCPCS Level II are alpha/alphanumeric (CMS).

Highest denial risk: 25, 59 (and X{EPSU}), 24, 57, 76/77, and 26/TC are repeat OIG audit targets — use only with supporting documentation.

Reference only — CPT descriptors are AMA-copyrighted and paraphrased here. Payer rules and payment percentages vary; verify against the current CPT codebook (Appendix A), the CMS HCPCS Level II file, and payer policy.

CPT numeric modifiers (AMA · CPT Appendix A)

22 — Increased Procedural Services — work substantially greater than typical. Requires documentation of the extra intensity/time/difficulty; supports an above-fee-schedule payment request. Not for E/M.

23 — Unusual Anesthesia — general anesthesia used where the procedure usually needs none or only local/regional. Anesthesia codes only.

24high-risk — Unrelated E/M During a Postoperative Period — same physician provides an E/M unrelated to the original surgery during its global period. Must link a clearly unrelated diagnosis.

25high-risk — Significant, Separately Identifiable E/M on the Same Day as a Procedure — E/M above and beyond the usual pre/post work of a same-day procedure. The single highest-misuse modifier; documentation must establish a service distinct from the procedure's inherent work.

26high-risk — Professional Component — bills only the physician's interpretation/supervision portion of a split (PC/TC) service. Valid only on PC/TC indicator '1' codes; the PC share varies by code per MPFS RVUs.

27 — Multiple Outpatient Hospital E/M Encounters on the Same Date — facility (hospital outpatient) use.

32 — Mandated Services — service required by a third party (e.g., a payer-mandated second opinion).

33 — Preventive Services — flags an ACA-designated preventive service so commercial payers waive cost-sharing. PT is the Medicare counterpart.

47 — Anesthesia by Surgeon — surgeon personally provided regional/general anesthesia. Not added to anesthesia codes; many payers give no extra payment.

50 — Bilateral Procedure — same procedure on both sides, same session. Typically pays 150% of the unilateral allowance. Report as one line/one unit. Not for codes already described as bilateral.

51 — Multiple Procedures — multiple procedures, same session, same provider. Triggers the multiple-procedure reduction (100%/50%/50%…). Not for add-on or 51-exempt codes.

52 — Reduced Services — service partially reduced or eliminated at provider discretion. Payment reduced.

53 — Discontinued Procedure — provider terminates a started procedure due to patient risk. Medicare commonly pays ~half. (ASC/hospital outpatient use 73/74 instead.)

54 — Surgical Care Only — surgeon does the operation; another provider does pre/post care. Paid the intra-operative percentage of the global package.

55 — Postoperative Management Only — provider furnishes only post-op care. Paid the post-op percentage.

56 — Preoperative Management Only — provider furnishes only pre-op care.

57high-risk — Decision for Surgery — E/M that led to the initial decision for a major (90-day global) surgery. Often confused with 25 (minor/same-day procedures).

58 — Staged or Related Procedure During Postoperative Period — planned/staged or more extensive procedure; a new global period begins.

59high-risk — Distinct Procedural Service — non-E/M service distinct from another same-day service (different site/session/lesion). Heavy OIG target; use only when no more specific X modifier fits.

62 — Two Surgeons (Co-Surgeons) — two surgeons each perform distinct parts; each paid 62.5% of the global fee. The MPFS co-surgeon indicator must be 1 or 2.

63 — Procedure on Infant Less Than 4 kg — indicates increased complexity/risk in neonates; supports increased payment. A 63-exempt code list applies.

66 — Surgical Team — more than two surgeons of different specialties. Paid by report; some payers pay 150% split among the team.

73 — Discontinued Outpatient/ASC Procedure Before Anesthesia — facility modifier; typically ~50% facility payment.

74 — Discontinued Outpatient/ASC Procedure After Anesthesia — facility modifier; full facility payment often allowed.

76high-risk — Repeat Procedure by Same Physician — same service repeated the same day by the same provider. Not for E/M.

77high-risk — Repeat Procedure by Another Physician — same service repeated by a different provider.

78 — Unplanned Return to the OR for a Related Procedure During the Postoperative Period — pays the intra-operative portion; does not restart the global period.

80 — Assistant Surgeon — physician assists throughout. Paid 16% of the surgical fee schedule (Medicare).

81 — Minimum Assistant Surgeon — physician provides minimal assistance.

82 — Assistant Surgeon (Qualified Resident Unavailable) — teaching-hospital setting; requires documentation that no qualified resident was available.

90 — Reference (Outside) Laboratory — test sent to and performed by an outside lab but billed by the ordering entity.

91 — Repeat Clinical Diagnostic Laboratory Test — medically necessary repeat of the same lab test, same day, for serial values. Not for re-running an abnormal result.

92 — Alternative Laboratory Platform Testing — test performed with a portable/handheld/kit platform.

93 — Synchronous Telemedicine via Audio-Only — real-time telephone-only service (added 2022). For Medicare audio-only behavioral health, FQ may be required instead.

95 — Synchronous Telemedicine via Audio and Video — real-time interactive audio-video; tied to CPT Appendix P eligible codes; reported with POS 02/10.

96 — Habilitative Services — services to develop skills not previously acquired (effective 1/1/2018; replaced the deleted SZ modifier).

97 — Rehabilitative Services — services to restore previously held skills lost to illness/injury (effective 1/1/2018).

99 — Multiple Modifiers — signals that several modifiers apply to one line.

Anesthesia physical status (P1–P6)

P1 — Normal healthy patient. 0 added units.

P2 — Mild systemic disease. 0 added units.

P3 — Severe systemic disease. Commonly +1 unit (commercial).

P4 — Severe systemic disease that is a constant threat to life. Commonly +2 units.

P5 — Moribund patient not expected to survive without the operation. Commonly +3 units.

P6 — Declared brain-dead patient whose organs are being removed for donation. 0 added units.

Category II performance measurement

1P — Measure not performed for medical reasons.

2P — Measure not performed for patient reasons.

3P — Measure not performed for system reasons.

8P — Measure not performed, reason not otherwise specified.

Anatomical / laterality (HCPCS Level II)

LT — Left side — identifies a procedure on the left of a paired structure.

RT — Right side — identifies a procedure on the right of a paired structure.

E1 — Upper left eyelid.

E2 — Lower left eyelid.

E3 — Upper right eyelid.

E4 — Lower right eyelid.

FA — Left thumb.

F1 — Left index finger.

F2 — Left middle finger.

F3 — Left ring finger.

F4 — Left little finger.

F5 — Right thumb.

F6 — Right index finger.

F7 — Right middle finger.

F8 — Right ring finger.

F9 — Right little finger.

TA — Left great toe.

T1 — Left second toe.

T2 — Left third toe.

T3 — Left fourth toe.

T4 — Left little toe.

T5 — Right great toe.

T6 — Right second toe.

T7 — Right third toe.

T8 — Right fourth toe.

T9 — Right little toe.

LC — Left circumflex coronary artery.

LD — Left anterior descending coronary artery.

LM — Left main coronary artery.

RC — Right coronary artery.

RI — Ramus intermedius coronary artery.

Ambulance arrangement (HCPCS Level II)

QM — Ambulance service provided under arrangement by a provider of services.

QN — Ambulance service furnished directly by a provider of services.

GM — Multiple patients transported on one ambulance trip.

Distinct-service X{EPSU} (replace 59 when one applies)

XEhigh-risk — Separate Encounter — distinct because it occurred during a separate encounter, same day.

XShigh-risk — Separate Structure — distinct because performed on a separate organ/structure.

XPhigh-risk — Separate Practitioner — distinct because performed by a different practitioner.

XUhigh-risk — Unusual Non-Overlapping Service — distinct because it does not overlap the main service's usual components.

Liability / ABN (HCPCS Level II)

GA — Waiver of liability (ABN) on file, required by payer policy — used when a denial is expected for lack of medical necessity; assigns liability to the beneficiary on denial. Don't combine with GX/GY/GZ.

GX — Voluntary ABN issued — for statutorily excluded/non-covered services where an ABN was given voluntarily.

GY — Statutorily excluded / not a Medicare benefit — forces an automatic denial (useful for secondary-payer billing). No ABN needed.

GZ — Expected to be denied as not reasonable/necessary; no ABN obtained — lines auto-deny and the patient is not held liable. Never bill with GA or GY.

Telehealth (HCPCS Level II)

GT — Via interactive audio-video — now mainly for Critical Access Hospital Method II institutional claims; CMS dropped GT for professional claims in 2018.

GQ — Via asynchronous (store-and-forward) telecommunications — historically tied to Alaska/Hawaii demonstrations; some Medicaid use.

FQ — Audio-only communication technology (Medicare behavioral health; FQHC/RHC). Active 2025/2026.

FR — Supervising practitioner present via real-time two-way audio-video (created 2022).

G0 — Telehealth for diagnosis/evaluation/treatment of acute stroke symptoms.

Therapy discipline & assistants

GP — Services delivered under a physical therapy plan of care.

GO — Services delivered under an occupational therapy plan of care.

GN — Services delivered under a speech-language pathology plan of care. (Only one discipline modifier per line — never stack GP/GO/GN.)

CQ — Service furnished in whole or part by a physical therapist assistant (PTA) — triggers 85% of the PT rate; required when a PTA furnishes more than 10% of a service (since 1/1/2020, alongside GP).

CO — Service furnished in whole or part by an occupational therapy assistant (OTA) — 85% payment alongside GO.

KX — Requirements specified in the medical policy have been met — for therapy, attests medical necessity above the annual KX threshold; also used in DMEPOS and CRC screening contexts.

Surgical / provider-role

AS — PA, NP, or CNS as assistant at surgery — must accompany 80/81/82. Medicare pays the assistant-at-surgery rate (16%), and NPP services at 85% of that.

GC — Service partly performed by a resident under a teaching physician (present for key portions).

GE — Resident service under the primary care exception (no teaching physician present).

FS — Split/shared E/M visit (facility settings) — bill under the NPI of the practitioner performing the substantive portion. Not for office/outpatient 99202–99215.

Q5 — Substitute physician under a reciprocal billing arrangement.

Q6 — Substitute physician under a fee-for-time ('locum tenens') arrangement — 60-day continuous limit (active-duty military exception).

Anesthesia provider

AA — Anesthesia personally performed by the anesthesiologist. 100%.

AD — Medical supervision, more than 4 concurrent procedures — reduced/fixed-unit payment (no time units).

QK — Medical direction of 2–4 concurrent procedures. 50%.

QY — Medical direction of one CRNA/AA by an anesthesiologist. 50%.

QX — CRNA/AA service with medical direction. 50%.

QZ — CRNA service without medical direction. 100% (CRNA-specific).

QS — Monitored anesthesia care (MAC) — informational; report actual time and a pricing modifier too.

G8 — MAC for a deep/complex/markedly invasive procedure — informational.

G9 — MAC for a patient with a severe cardiopulmonary history — informational.

Drug modifiers

JW — Drug amount discarded/not administered (single-dose vial/package wastage) — billed on a separate line for the wasted units.

JZ — Zero drug amount discarded — required since 7/1/2023; single-dose drug claims without JW or JZ may be returned as unprocessable for DOS on/after 10/1/2023.

JG — 340B-acquired drug (legacy) — no longer valid for 340B reporting for DOS on/after 1/1/2025.

TB — 340B-acquired drug (informational) — all 340B covered entities must report TB beginning 1/1/2025. No payment reduction.

Medicare-specific / other

PT — Colorectal screening converted to diagnostic/therapeutic — Medicare only; waives the deductible. Coinsurance phasing out (15% 2023–2026, 10% 2027–2029, 0% from 2030).

CR — Catastrophe/Disaster Related — Part B flag during declared emergencies/Section-1135 waivers. Use only during an active declared event.

CS — Cost-sharing waived — a COVID-19 PHE mechanism (FFCRA). Do not use outside an active waiver.

QW — CLIA-waived test — must be first-listed; a valid CLIA certificate number must appear on the claim. No payment change; prevents denials.

GV — Attending physician not employed by or under arrangement with the hospice (related care, Part B, attending only).

GW — Service unrelated to the hospice patient's terminal condition (facility claims use Condition Code 07 instead).

PO — Excepted services at an off-campus provider-based outpatient department (grandfathered; full OPPS rate).

PN — Non-excepted off-campus provider-based department — triggers the lower site-neutral/MPFS-equivalent rate. Don't report PO and PN on the same line.

PA — Surgical 'never event': wrong body part. Non-covered; related lines are reviewed/denied.

PB — Surgical 'never event': wrong patient. Non-covered.

PC — Surgical 'never event': wrong surgery. Non-covered. (Do not confuse with modifier 26, professional component.)

MX — Inpatient 'never event': wrong surgery.

MY — Inpatient 'never event': wrong body part.

MZ — Inpatient 'never event': wrong patient.

SG — ASC facility service (distinguishes facility from professional charge). Largely phased out for Medicare; some commercial payers still reference it.

TChigh-risk — Technical Component — equipment/supplies/technical staff portion of a split service; TC + 26 = the global service. Valid only on PC/TC indicator '1' codes; the split varies by code per MPFS RVUs.

FX — X-ray taken using film — 20% technical-component reduction.

FY — Computed (cassette-based) radiography — 10% technical-component reduction (since CY2023).

CT — CT performed on non-NEMA-XR-29-compliant equipment — 15% reduction.

Additional HCPCS Level II modifiers (CMS)

21 — Prolonged evaluation and management services

60 — Altered surgical field

A1 — Dressing for one wound

A2 — Dressing for two wounds

A3 — Dressing for three wounds

A4 — Dressing for four wounds

A5 — Dressing for five wounds

A6 — Dressing for six wounds

A7 — Dressing for seven wounds

A8 — Dressing for eight wounds

A9 — Dressing for nine or more wounds

AE — Registered dietician

AF — Specialty physician

AG — Primary physician

AH — Clinical psychologist

AI — Principal physician of record

AJ — Clinical social worker

AK — Non-participating physician

AM — Physician, team member service

AO — Provider declined alternate payment method

AP — No determination of refractive state

AQ — Physician service in an unlisted HPSA area

AR — Physician scarcity area

AT — Acute treatment

AU — Urological, ostomy, or tracheostomy item

AV — Item with prosthetic/orthotic

AW — Item with a surgical dressing

AX — Item with dialysis services

AY — Item/service not for ESRD treatment

AZ — Physician service in a dental HPSA

BA — Item with PEN services

BL — Special acquisition of blood products

BO — Nutrition oral administration, no tube

BP — Beneficiary elected to purchase item

BR — Beneficiary elected to rent item

BU — Beneficiary undecided on purchase/rent

CA — Procedure payable inpatient

CB — ESRD beneficiary Part A SNF — separate payment

CC — Procedure code change

CD — AMCC test for ESRD or MCP physician

CE — Medically necessary AMCC test, separately reimbursable

CF — AMCC test not composite rate

CG — Policy criteria applied

CH — 0 percent impaired, limited, restricted

CI — 1 to <20 percent impaired

CJ — 20 to <40 percent impaired

CK — 40 to <60 percent impaired

CL — 60 to <80 percent impaired

CM — 80 to <100 percent impaired

CN — 100 percent impaired, limited

CP — Adjunctive service related to a C-APC service

DA — Oral health assessment, not by dentist

EA — ESA, anemia, chemo-induced

EB — ESA, anemia, radio-induced

EC — ESA, anemia, non-chemo/radio

ED — HCT >39% or Hgb >13g, >=3 cycles

EE — HCT >39% or Hgb >13g, <3 cycles

EJ — Subsequent claim

EM — Emergency reserve supply (ESRD)

EP — Medicaid EPSDT program service

ET — Emergency services

EX — Expatriate beneficiary

EY — No physician order for item/service

FB — Item provided without cost

FC — Partial credit, replaced device

FP — Service part of a family planning program

G1 — URR reading of less than 60

G2 — URR reading of 60 to 64.9

G3 — URR reading of 65 to 69.9

G4 — URR reading of 70 to 74.9

G5 — URR reading of 75 or greater

G6 — ESRD patient <6 dialysis/month

G7 — Payment limits do not apply

GB — Claim resubmitted

GD — Units of service exceed MUE value

GF — Non-physician service in a critical access hospital

GG — Payment screening mammography plus diagnostic mammography

GH — Diagnostic mammography converted from screening mammography

GJ — Opt-out provider of emergency service

GK — Actual item/service ordered (reasonable and necessary)

GL — Upgraded item, no charge

GR — Service performed by a VA resident

GS — EPO/darbepoetin reduced 25%

GU — Liability waiver, routine notice

H9 — Court-ordered

HA — Child/adolescent program

HB — Adult program, non-geriatric

HC — Adult program, geriatric

HD — Pregnant/parenting program

HE — Mental health program

HF — Substance abuse program

HG — Opioid addiction treatment program

HH — Mental health/substance abuse program

HI — Mental health/intellectual & developmental disability program

HJ — Employee assistance program

HK — Specialized high-risk mental health population program

HL — Intern

HM — Less than bachelor degree level

HN — Bachelor's degree level

HO — Master's degree level

HP — Doctoral level

HQ — Group setting

HR — Family/couple with client present

HS — Family/couple without client present

HT — Multi-disciplinary team

HU — Child welfare agency funded

HV — Funded by state addiction agency

HW — State mental health agency funded

HX — County/local agency funded

HY — Funded by juvenile justice

HZ — Criminal justice agency funded

J1 — CAP no-pay submission for a prescription number

J2 — CAP restocking of emergency drugs

J3 — CAP drug unavailable through the CAP, furnished under another methodology

J4 — DMEPOS competitive bid item furnished by a hospital

JA — Administered intravenously

JB — Administered subcutaneously

JC — Skin substitute graft

JD — Skin substitute not used as a graft

JE — Administered via dialysate

K0 — Lower extremity prosthesis functional level 0

K1 — Lower extremity prosthesis functional level 1

K2 — Lower extremity prosthesis functional level 2

K3 — Lower extremity prosthesis functional level 3

K4 — Lower extremity prosthesis functional level 4

KA — Wheelchair add-on option/accessory

KB — More than 4 modifiers on a claim (beneficiary-requested upgrade)

KC — Replacement of special power wheelchair interface

KD — Drug/biological infused through DME

KE — Bid under round 1 of the DMEPOS competitive bidding program

KF — FDA class III device

KG — DMEPOS competitive bid program number 1

KH — DMEPOS initial claim, purchase or first-month rental

KI — DMEPOS second or third month rental

KJ — DMEPOS PEN pump or capped-rental months 4–15

KK — DMEPOS competitive bid program number 2

KL — DMEPOS mail-order competitive bid

KM — Replacement facial prosthesis, new impression

KN — Replacement facial prosthesis, old model

KO — Single drug unit-dose form

KP — First drug of a multi-drug unit-dose

KQ — Second/subsequent drug of a multi-drug unit-dose

KR — Rental item, partial month

KS — Glucose monitor supply for a non-insulin-treated diabetic

KT — Item from a non-contract supplier

KU — DMEPOS competitive bid program number 3

KV — DMEPOS item, professional service

KW — DMEPOS competitive bid program number 4

KY — DMEPOS competitive bid program number 5

KZ — New coverage not implemented by Medicare Advantage

LL — Lease/rental (applied to purchase)

LR — Laboratory round trip

LS — FDA-monitored intraocular lens implant

M2 — Medicare secondary payer

MS — 6-month maintenance/service fee for parts/labor

NB — Drug-specific nebulizer

NR — New when rented

NU — New equipment

PD — Inpatient admission within 3 days

PI — PET, tumor initial treatment strategy

PL — Progressive addition lenses

PM — Post-mortem

PS — PET, tumor subsequent treatment strategy

Q0 — Investigational clinical research service

Q1 — Routine clinical research service

Q2 — Demonstration procedure/service

Q3 — Live kidney donor surgery and related services

Q4 — Service exempt from ordering/referring physician requirements

Q7 — One Class A finding

Q8 — Two Class B findings

Q9 — One Class B and two Class C findings

QC — Single-channel monitoring

QD — Recording/storage in solid-state memory

QE — Prescribed amount of oxygen is less than 1 LPM

QF — Prescribed oxygen >4 LPM and portable oxygen prescribed

QG — Prescribed amount of oxygen is greater than 4 LPM

QH — Oxygen-conserving device with an oxygen delivery system

QJ — Services to a prisoner in state/local custody

QL — Patient pronounced dead after the ambulance is called

QP — Individually ordered lab test

QT — Recording/storage on a tape analog recorder

RA — Replacement of a DME, orthotic, or prosthetic item

RB — Replacement part of a DME, orthotic, or prosthetic item

RD — Drug provided to a beneficiary but not administered incident-to

RE — Furnished in full compliance with a REMS

RR — Rental (DME)

SA — Nurse practitioner with physician

SB — Nurse midwife

SC — Medically necessary service or supply

SD — Services provided by a home infusion RN

SE — State/federally funded program/service

SF — Second opinion ordered by a PRO

SH — Second concurrent infusion therapy

SJ — Third concurrent infusion therapy

SK — Member of a high-risk population

SL — State-supplied vaccine

SM — Second opinion

SN — Third opinion

SQ — Item ordered by home health

SS — Home infusion therapy in an infusion suite

ST — Related to trauma or injury

SU — Procedure performed in a physician's office

SV — Drugs delivered but not used

SW — Service by a certified diabetic educator

SY — Contact with a high-risk population

SZ — Habilitative services

TD — Registered nurse

TE — LPN/LVN

TF — Intermediate level of care

TG — Complex/high-tech level of care

TH — Obstetrical treatment/service, prenatal or postpartum

TJ — Child/adolescent program, group

TK — Extra patient or passenger

TL — Early intervention IFSP

TM — Individualized education program (IEP)

TN — Rural/out-of-service area

TP — Medical transport, unloaded vehicle

TQ — BLS by a volunteer ambulance provider

TR — School-based IEP out of district

TT — Additional patient

TU — Overtime payment rate

TV — Holiday/weekend payment rate

TW — Back-up equipment

U1 — Medicaid level of care 1, state-defined

U2 — Medicaid level of care 2, state-defined

U3 — Medicaid level of care 3, state-defined

U4 — Medicaid level of care 4, state-defined

U5 — Medicaid level of care 5, state-defined

U6 — Medicaid level of care 6, state-defined

U7 — Medicaid level of care 7, state-defined

U8 — Medicaid level of care 8, state-defined

U9 — Medicaid level of care 9, state-defined

UA — Medicaid level of care 10, state-defined

UB — Medicaid level of care 11, state-defined

UC — Medicaid level of care 12, state-defined

UD — Medicaid level of care 13, state-defined

UE — Used durable medical equipment

UF — Services provided in the morning

UG — Services provided in the afternoon

UH — Services provided in the evening

UJ — Services provided at night

UK — Service on behalf of the client to someone other than the client (collateral)

UN — Two patients served

UP — Three patients served

UQ — Four patients served

UR — Five patients served

US — Six or more patients served

V1 — Demonstration modifier 1

V2 — Demonstration modifier 2

V3 — Demonstration modifier 3

V5 — Any vascular catheter

V6 — Arteriovenous graft

V7 — Arteriovenous fistula

VP — Aphakic patient

ZA — Novartis/Sandoz

ZB — Pfizer/Hospira

Genetic & molecular testing modifiers (Category I, gene-specific)

0A — BRCA1 (hereditary breast/ovarian cancer)

0B — BRCA2 (hereditary breast cancer)

0C — Neurofibromin (neurofibromatosis, type 1)

0D — Merlin (neurofibromatosis, type 2)

0E — C-RET (MEN types 2A/B, familial medullary thyroid carcinoma)

0F — VHL (von Hippel-Lindau disease, renal carcinoma)

0G — SDHD (hereditary paraganglioma)

0H — SDHB (hereditary paraganglioma)

0I — ERRB2, HER-2/neu

0J — MLH1 (HNPCC, mismatch repair genes)

0K — MSH2, MSH6, or PMS2 (HNPCC, mismatch repair genes)

0L — APC (hereditary polyposis coli)

0M — RB (retinoblastoma)

0N — TP53, p53

0O — PTEN (Cowden's syndrome)

0P — KIT, CD117 (GIST)

0Z — Solid tumor gene, NOS

1A — WT1 or WT2 (Wilm's tumor)

1B — PAX3, PAX7, or FOXO1A (alveolar rhabdomyosarcoma)

1C — FLI1, ERG, ETV1, or EWSR1 (Ewing's sarcoma, desmoplastic round cell)

1D — DDIT3 or FUS (myxoid liposarcoma)

1E — NR4A3, RBF56, or TCF12 (myxoid chondrosarcoma)

1F — SSX1, SSX2, or SYT (synovial sarcoma)

1G — MYCN (neuroblastoma)

1H — COL1A1 or PDGFB (dermatofibrosarcoma protruberans)

1I — TFE3 or ASPSCR1 (alveolar soft parts sarcoma)

1J — JAZF1 or JJAZ1 (endometrial stromal sarcoma)

1Z — Sarcoma gene, NOS

2A — RUNX1 or CBFA2T1 (AML1/ETO)

2B — BCR or ABL1

2C — PBX1 or TCF3, CGF1

2D — CBFB or MYH11

2E — MLL (acute leukemia)

2F — PML or RARA

2G — ETV6, TEL

2H — BCL2 (lymphoma)

2I — CCND1, BCL1, cyclin D1 (mantle cell lymphoma, myeloma)

2J — MYC (Burkitt lymphoma), c-MYC (lymphoma)

2K — IGH (lymphoma/leukemia)

2L — IGK (lymphoma/leukemia)

2M — TRB, T cell receptor beta (lymphoma/leukemia)

2N — TRG, T cell receptor gamma (lymphoma/leukemia)

2O — SIL or TAL1 (T cell leukemia)

2Q — API1 or MALT1 (MALT lymphoma)

2R — NPM or ALK (anaplastic large cell lymphoma)

2S — FLT3 (acute myelogenous leukemia)

2T — BCL6 (B cell lymphoma)

2Z — Lymphoid/hematopoietic neoplasia, NOS

3A — Factor V (Leiden, others) (hypercoagulable state)

3B — FACC (Fanconi anemia)

3C — FACD (Fanconi anemia)

3D — HBB, beta globin (thalassemia, sickle cell anemia, other hemoglobinopathies)

3E — HBA, alpha globin (thalassemia)

3F — MTHFR (elevated homocystinemia)

3G — Prothrombin (factor II, 20210A) (hypercoagulable state)

3H — Factor VIII (hemophilia A/vWF)

3I — Factor IX (hemophilia B)

3K — Factor XIII (bleeding or hypercoagulable state)

3Z — Non-neoplastic hematology/coagulation, NOS

4A — HLA-A

4B — HLA-B

4C — HLA-C

4E — HLA-DRB all

4F — HLA-DQB1

4G — HLA-DPB1

4H — Kell

4I — Fingerprint for engraftment

4J — Fingerprint for donor allelotype

4K — Fingerprint for recipient allelotype

4L — Fingerprint for leukocyte chimerism

4M — Fingerprint for maternal vs fetal origin

4N — Microsatellite instability

4O — Microsatellite loss (loss of heterozygosity)

4P — HLA-DRB1

4Q — HLA-DRB3

4R — HLA-DRB4

4S — HLA-DRB5

4T — HLA-DQA1

4U — HLA-DPA1

4Z — Histocompatibility/blood typing, NOS

5A — ASPA, aspartoacylase A (Canavan disease)

5B — FMR-1 (Fragile X, FRAXA, syndrome)

5C — FRDA, frataxin (Friedreich ataxia)

5D — HD (Huntington's disease)

5E — GABRA5, NIPA1, UBE3A, or ANCR GABRA (Prader Willi-Angelman syndrome)

5F — GJB2, connexin-26 (hereditary hearing loss)

5G — GJB1, connexin-32 (X-linked Charcot-Marie-Tooth disease)

5H — SNRPN (Prader Willi-Angelman syndrome)

5I — SCA1, ataxin-1 (spinocerebellar ataxia, type 1)

5J — SCA2, ataxin-2 (spinocerebellar ataxia, type 2)

5K — MJD, ataxin-3 (spinocerebellar ataxia, type 3, Machado-Joseph disease)

5L — CACNA1A (spinocerebellar ataxia, type 6)

5M — ATXN7, ataxin-7 (spinocerebellar ataxia, type 7)

5N — PMP-22 (Charcot-Marie-Tooth disease, type 1A)

5O — MECP2 (Rett syndrome)

5Z — Neurologic, non-neoplastic, NOS

6A — DMD, dystrophin (Duchenne/Becker muscular dystrophy)

6B — DMPK (myotonic dystrophy, type 1)

6C — ZNF-9 (myotonic dystrophy, type 2)

6D — SMN1/SMN2 (autosomal recessive spinal muscular atrophy)

6E — MTTK, tRNAlys (myotonic epilepsy, MERRF)

6F — MTTL1, tRNAleu (mitochondrial encephalomyopathy, MELAS)

6Z — Muscular, NOS

7A — APOE, apolipoprotein E (cardiovascular disease or Alzheimer's)

7B — NPC1 or NPC2, sphingomyelin phosphodiesterase (Niemann-Pick disease)

7C — GBA, acid beta glucosidase (Gaucher disease)

7D — HFE (hemochromatosis)

7E — HEXA, hexosaminidase A (Tay-Sachs disease)

7F — ACADM (medium chain acyl CoA dehydrogenase deficiency)

7Z — Metabolic, other, NOS

8A — CFTR (cystic fibrosis)

8B — PRSS1 (hereditary pancreatitis)

8Z — Metabolic, transport, NOS

9A — TPMT (thiopurine methyltransferase) (patients on antimetabolite therapy)

9B — CYP2 genes, cytochrome P450 (drug metabolism)

9C — ABCB1, MDR1 or P-glycoprotein (drug transport)

9D — NAT2 (drug metabolism)

9L — Metabolic-pharmacogenetics, NOS

9M — FGFR1 (Pfeiffer and Kallman syndromes)

9N — FGFR2 (Crouzon, Jackson-Weiss, Apert, Saethre-Chotzen syndromes)

9O — FGFR3

9P — TWIST (Saethre-Chotzen syndrome)

9Q — DGCR, CATCH-22 (DiGeorge and 22q11 deletion syndromes)

9Z — Dysmorphology, NOS

No modifiers match your search.

Frequently asked questions

What is a modifier in medical billing?

A two-character code appended to a CPT or HCPCS code that adds detail without changing the code's meaning — e.g., that a service was bilateral (50), distinct (59), or telehealth (95). Modifiers affect payment and prevent denials.

What is the difference between CPT and HCPCS modifiers?

CPT (Level I) modifiers are two-digit numeric codes (plus P1–P6 and Category II) maintained by the AMA. HCPCS Level II modifiers are alpha or alphanumeric and maintained by CMS.

Which modifiers cause the most denials?

Modifiers 25 and 59 (and the X{EPSU} set), plus 24, 57, 76/77 and 26/TC, are repeat OIG audit targets. Use them only with documentation that supports a distinct or separately identifiable service.

What is the difference between modifier 25 and 57?

Modifier 25 is for a significant, separate E/M on the same day as a minor procedure. Modifier 57 is for the E/M that led to the decision for a major (90-day global) surgery. Mismatching them against the global period triggers automatic denials.

When should I use an X modifier instead of 59?

Use XE (separate encounter), XS (separate structure), XP (separate practitioner), or XU (unusual non-overlapping) whenever one specifically applies; reserve 59 for when none fits.

Sources: AMA CPT Appendix A; CMS HCPCS Level II file and Medicare Claims Processing Manual; MAC bulletins (Noridian, Palmetto); HHS-OIG. Descriptions paraphrased. Last reviewed June 2026.