Medical Billing Terms B: CMS-1500 Boxes 1a to 24H
This page explains CMS-1500 (1500 claim form) boxes 1a through 24H in plain English, using the NUCC instruction manual as the source. Each entry gives a plain definition, why it matters, an example, and an official source. MCM South Medical Billing Service, LLC works only in mental and behavioral health billing.
On this page (19 terms)
- Box 11 (Insured's Policy, Group, or FECA Number)
- Box 11d (Another Health Benefit Plan)
- Box 12 (Patient or Authorized Person's Signature)
- Box 13 (Insured's or Authorized Person's Signature)
- Box 14 (Date of Current Illness, Injury, or Pregnancy)
- Box 17 (Name of Referring Provider or Other Source)
- Box 19 (Additional Claim Information)
- Box 1a (Insured's ID Number)
- Box 21 (Diagnosis or Nature of Illness or Injury)
- Box 22 (Resubmission and Original Reference Number)
- Box 23 (Prior Authorization Number)
- Box 24A (Dates of Service)
- Box 24B (Place of Service)
- Box 24C (EMG)
- Box 24D (Procedures, Services, or Supplies)
- Box 24E (Diagnosis Pointer)
- Box 24F (Charges)
- Box 24G (Days or Units)
- Box 24H (EPSDT/Family Plan)
How to use these CMS-1500 box 21 definitions
Use this page as a quick reference for CMS-1500 box 21, from Box 11 to Box 24H. Each entry gives a plain definition, why it matters to a mental health practice, and an official source. When a rule changes by payer or state, the entry says so, so confirm CMS-1500 box 21 details with the payer before you bill.
Checklist: put the cms-1500 box 21 definitions to work
- Check the cms-1500 box 21 entries above before you send a claim that depends on them.
- Share this cms-1500 box 21 page with front-desk and billing staff so everyone works from the same definitions.
- When a payer letter mentions cms-1500 box 21, find the matching entry and note the date you checked it.
- Keep your cms-1500 box 21 notes next to your payer contracts, because a contract can define a term differently.
- Ask the payer to confirm in writing how it applies cms-1500 box 21 before you change a workflow.
- Train new staff on cms-1500 box 21 first, then move on to the rest of the glossary.
- Log any cms-1500 box 21 question that comes up twice, then add the answer to your billing procedures.
- Use the source links under the cms-1500 box 21 entries to confirm the current rule.
- Print the cms-1500 box 21 entries you use most and keep them at the billing desk.
- Review your cms-1500 box 21 notes each quarter, because payer and CMS rules change.
- Mark where cms-1500 box 21 work differently for psychotherapists and for psychiatrists in your own procedures.
- If a cms-1500 box 21 entry does not match what your payer tells you, follow the payer contract and ask for the answer in writing.
- A common cms-1500 box 21 mistake is relying on an old payer bulletin, so check the date on every source.
Box 11 (Insured's Policy, Group, or FECA Number)
Also called CMS-1500 box 11; item 11; group number on claim
- Definition
- Box 11 on the 1500 claim form holds the insured's policy, group, or FECA number. It is the alphanumeric identifier for health, auto, or other insurance coverage.
- Why it matters
- The group number helps the payer find the right employer plan. Copy it from the card exactly. Follow the payer's instruction on whether to use Box 11 for a plan with no group number.
- Illustrative example
- A biller copies the group number from the insurance card into Box 11.
Related termsGroup NumberBox 1a (Insured's ID Number)Insurance CardMember ID
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims ProcessingEligibility & Benefits
Box 11d (Another Health Benefit Plan)
Also called CMS-1500 box 11d; item 11d; is there another health benefit plan
- Definition
- Box 11d on the 1500 claim form asks whether the patient has insurance coverage other than the plan named in Box 1.
- Why it matters
- A yes answer tells the payer to expect a secondary payer. If yes, complete Box 9 through Box 9d. Payers use the answer to coordinate benefits.
- Illustrative example
- A patient has a spouse's plan as a secondary, so the biller answers yes and completes Box 9.
Related termsBox 9 (Other Insured's Information)Secondary InsuranceCoordination of Benefits (COB)Primary Insurance
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims ProcessingEligibility & Benefits
Box 12 (Patient or Authorized Person's Signature)
Also called CMS-1500 box 12; item 12; signature on file SOF; release of information
- Definition
- Box 12 on the 1500 claim form is the patient's or authorized person's signature, which authorizes release of the medical or other information needed to process the claim.
- Why it matters
- A payer expects a signed release on file. Many practices enter "Signature on File" when they hold a signed authorization. Keep the signed form in the record.
- Illustrative example
- A practice has a signed release in the chart and enters Signature on File in Box 12.
Related termsSignature on File (SOF)Box 13 (Insured's or Authorized Person's Signature)Assignment of Benefits (AOB)Documentation
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims ProcessingAudits & Compliance
Box 13 (Insured's or Authorized Person's Signature)
Also called CMS-1500 box 13; item 13; assignment of benefits signature; authorization of payment
- Definition
- Box 13 on the 1500 claim form is the insured's or authorized person's signature, which authorizes payment of medical benefits to the provider.
- Why it matters
- This is how an assignment of benefits is shown on the claim. Without it, a payer may pay the patient instead of the practice. Keep the signed assignment on file.
- Illustrative example
- A patient signs the assignment on intake forms, and Box 13 shows Signature on File so the plan pays the practice.
Related termsAssignment of Benefits (AOB)Signature on File (SOF)Box 12 (Patient or Authorized Person's Signature)Payer of Last Resort
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims ProcessingPayment & Reimbursement
Box 14 (Date of Current Illness, Injury, or Pregnancy)
Also called CMS-1500 box 14; item 14; date of onset
- Definition
- Box 14 on the 1500 claim form identifies the first date of onset of the illness, the date of injury, or the last menstrual period for pregnancy.
- Why it matters
- Some payers ask for it, and it can matter for accident-related claims. Do not guess; use it only when it is known and payer rules call for it.
- Illustrative example
- A billing team enters the onset date for an accident-related trauma condition when the payer requires it.
Related termsBox 10 (Condition Related To)Date of Service (DOS)Claim FormDocumentation
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims Processing
Box 17 (Name of Referring Provider or Other Source)
Also called CMS-1500 box 17; item 17; referring provider; ordering provider; supervising provider
- Definition
- Box 17 on the 1500 claim form shows the name of the referring, ordering, or supervising provider who directed or ordered the service. Box 17a holds a non-NPI identifier and Box 17b holds the NPI.
- Why it matters
- Some payers, plans, and referral-based benefits require a referring provider, and supervised clinicians may need a supervising provider listed. A missing or invalid referring NPI is a common rejection.
- Illustrative example
- A plan requires a referral for therapy, so the biller enters the referring physician's name and NPI in Box 17 and Box 17b.
Related termsReferring ProviderReferralSupervising ProviderNPI (National Provider Identifier)
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims Processing
Box 19 (Additional Claim Information)
Also called CMS-1500 box 19; item 19; additional claim information
- Definition
- Box 19 on the 1500 claim form holds additional claim information designated by NUCC and required by the payer.
- Why it matters
- Payers use it for special information. Use only what the payer instructs, and use the qualifier the payer names.
- Illustrative example
- A payer asks for a specific note in Box 19 on a corrected claim, and the biller enters it as instructed.
Related termsCorrected ClaimClaim AttachmentBox 22 (Resubmission and Original Reference Number)Payer Portal
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims Processing
Box 1a (Insured's ID Number)
Also called CMS-1500 box 1a; item 1a; insured's ID; member ID on claim
- Definition
- Box 1a on the 1500 claim form holds the insured's ID number. It identifies the insured to the payer.
- Why it matters
- A wrong or truncated ID is a leading cause of eligibility rejections. Copy the ID exactly as printed on the card, including any alpha prefix, and use the format the payer requires.
- Illustrative example
- A biller copies the alpha prefix and the ID from the card into Box 1a and the claim passes the payer's front-end edits.
Related termsMember IDAlpha PrefixInsurance CardEligibility Denial
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims ProcessingEligibility & Benefits
Box 21 (Diagnosis or Nature of Illness or Injury)
Also called CMS-1500 box 21; item 21; ICD-10 diagnosis codes; ICD indicator
- Definition
- Box 21 on the 1500 claim form lists the diagnosis codes for the sign, symptom, complaint, or condition related to the services. It also holds the ICD indicator, which is 0 for ICD-10-CM.
- Why it matters
- Diagnosis codes support medical necessity. Each service line points back to a letter in Box 21. Code to the highest specificity, and list the primary diagnosis first.
- Illustrative example
- A therapist lists F41.1 as diagnosis A in Box 21, and 90834 points to A.
Related termsICD-10-CMDiagnosis PointerPrimary DiagnosisMedical Necessity
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)CMS ICD-10checked 10/9/26
CategoriesClaims Processing
Box 22 (Resubmission and Original Reference Number)
Also called CMS-1500 box 22; item 22; resubmission code; frequency code 7 8; corrected claim box
- Definition
- Box 22 on the 1500 claim form holds the resubmission code and the payer's original reference number for a claim you send again. NUCC lists code 7 for replacement of a prior claim and code 8 for void or cancel of a prior claim.
- Why it matters
- Use the correct code and the original claim number, or the payer may reject the new claim as a duplicate. Follow the payer's instructions for corrected claims.
- Illustrative example
- A biller corrects a wrong unit count, enters code 7 and the payer's claim number in Box 22, and resubmits.
Related termsCorrected ClaimReplacement ClaimVoid ClaimInternal Control Number (ICN)Guide: Corrected claims
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims Processing
Box 23 (Prior Authorization Number)
Also called CMS-1500 box 23; item 23; prior auth number; referral number on claim
- Definition
- Box 23 on the 1500 claim form holds the payer-assigned number that authorizes the services or the referral.
- Why it matters
- Claims for services that need authorization can be denied without a valid number. Enter it exactly, and check the authorized dates and units before you bill.
- Illustrative example
- A payer authorizes 12 sessions, and the biller enters the authorization number in Box 23 on each claim.
Related termsAuthorization NumberPrior AuthorizationAuthorized UnitsAuthorization Denial
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
Box 24A (Dates of Service)
Also called CMS-1500 box 24A; item 24A; date of service on claim line
- Definition
- Box 24A on the 1500 claim form shows the month, day, and year each service was provided. It is entered for each service line.
- Why it matters
- The date must match the note. A wrong date can cause a denial, a timely filing problem, or a duplicate rejection.
- Illustrative example
- A biller enters each session date from the schedule and checks it against the signed note.
Related termsDate of Service (DOS)Timely FilingDuplicate ClaimProgress Note
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims Processing
Box 24B (Place of Service)
Also called CMS-1500 box 24B; item 24B; POS on claim line
- Definition
- Box 24B on the 1500 claim form identifies the location where the service was provided, using a two-digit place of service code.
- Why it matters
- The code affects payment and telehealth rules, such as POS 02 or POS 10 for telehealth and POS 11 for an office. Use the code that matches where the service happened and the payer's policy.
- Illustrative example
- A therapist sees a client by video while the client is at home. The biller enters the telehealth place of service code the payer requires.
Related termsPlace of Service (POS)Place of Service 10Place of Service 02Telehealth Modifier 95
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)CMS Place of Service Code Setchecked 10/9/26
CategoriesClaims ProcessingTelehealth Terms
Box 24C (EMG)
Also called CMS-1500 box 24C; item 24C; emergency indicator
- Definition
- Box 24C on the 1500 claim form identifies whether the service was an emergency. Payers give their own instructions for it.
- Why it matters
- Most outpatient behavioral health claims leave it blank unless a payer instructs otherwise. A wrong entry can affect payment.
- Illustrative example
- A biller leaves Box 24C blank for a routine therapy claim, as the payer's manual directs.
Related termsClaim FormModifierPlace of Service (POS)Box 24D (Procedures, Services, or Supplies)
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims Processing
Box 24D (Procedures, Services, or Supplies)
Also called CMS-1500 box 24D; item 24D; CPT code and modifier on claim line
- Definition
- Box 24D on the 1500 claim form identifies the medical services and procedures provided, using CPT or HCPCS codes and up to four modifiers.
- Why it matters
- This is where the code and any modifier go. A code or modifier mismatch with the note is a common denial cause. Enter add-on codes on the same claim as the base service.
- Illustrative example
- A psychiatrist enters 99214 with modifier 25 and +90833 on separate lines of the same claim.
Related termsCPT CodeHCPCS (Healthcare Common Procedure Coding System)ModifierModifier 25
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims Processing
Box 24E (Diagnosis Pointer)
Also called CMS-1500 box 24E; item 24E; diagnosis pointer on claim line
- Definition
- Box 24E on the 1500 claim form holds the diagnosis pointer, which is the letter or letters from Box 21 that show why the service was performed.
- Why it matters
- A bad pointer links the service to the wrong diagnosis and can cause a medical necessity denial. Point each line to the diagnosis that supports it.
- Illustrative example
- The biller points 90837 to diagnosis A in Box 24E because A is the diagnosis treated in the session.
Related termsDiagnosis PointerBox 21 (Diagnosis or Nature of Illness or Injury)Medical NecessityCoding Denial
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims Processing
Box 24F (Charges)
Also called CMS-1500 box 24F; item 24F; billed charge per line
- Definition
- Box 24F on the 1500 claim form holds the total billed amount for each service line.
- Why it matters
- Billed charges usually follow your fee schedule. Payers pay by their own allowed amount, not your billed charge, but the number must be right.
- Illustrative example
- A practice enters its standard fee for each service line, and the payer adjusts to its allowed amount.
Related termsBilled ChargeAllowed AmountFee ScheduleContractual Adjustment
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims ProcessingPayment & Reimbursement
Box 24G (Days or Units)
Also called CMS-1500 box 24G; item 24G; units on claim line
- Definition
- Box 24G on the 1500 claim form holds the number of days or units of service, as defined in the CPT or HCPCS manuals.
- Why it matters
- Wrong units cause denials and underpayments. Time-based add-ons and testing codes are billed in units. Check the MUE limit for the code.
- Illustrative example
- A psychologist bills 96136 with one unit and +96137 with two units.
Related termsUnitsMedically Unlikely Edit (MUE)CPT 96137Underpayment
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)checked 10/9/26
CategoriesClaims Processing
Box 24H (EPSDT/Family Plan)
Also called CMS-1500 box 24H; item 24H; EPSDT indicator
- Definition
- Box 24H on the 1500 claim form identifies certain services covered under some state Medicaid plans, including Early and Periodic Screening, Diagnostic, and Treatment services.
- Why it matters
- Only some Medicaid plans require it. Check the state Medicaid or MCO billing manual, since instructions vary by state.
- Illustrative example
- A biller checks the state Medicaid manual to see if Box 24H is required for a child's screening visit.
Related termsEPSDTMedicaidMedicaid Managed Care Organization (MCO)Claim Form
Reference sourceNUCC, 1500 Claim Form Reference Instruction Manual, Version 13.0 (7/25)Medicaid.govchecked 10/9/26
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Quick answer: CMS-1500 box 21
What is a diagnosis pointer on a CMS-1500?
It is the letter or letters in Box 24E that point to the diagnosis in Box 21 supporting each service line. A wrong pointer can cause a medical necessity denial.
Frequently asked questions: CMS-1500 box 21
What goes in Box 21 of the CMS-1500?
Box 21 lists the diagnosis codes related to the services, with the ICD indicator, which is 0 for ICD-10-CM. Each service line points back to a letter in Box 21.
What is Box 22 used for?
Box 22 holds the resubmission code and the payer's original reference number when you send a claim again. NUCC lists code 7 for a replacement claim and code 8 for a void.
What is Box 24B on the claim form?
Box 24B holds the two-digit place of service code. It affects payment and telehealth rules, so use the code that matches where the service happened and the payer's policy.
Related resources
Where MCM South works
MCM South serves psychotherapists and psychiatrists in ten states: Georgia, Massachusetts, Connecticut, Texas, Florida, New York, Colorado, Tennessee, North Carolina and Illinois.
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