UB04 Type of Bill Code 0121: Hospital Inpatient (Medicare Part B only) - Admit through Discharge Claim

Overview

Code 0121 is a Type of Bill (TOB) used on the UB-04 claim form to identify a Hospital Inpatient (Medicare Part B only) claim that covers the entire stay from admission through discharge. The code structure breaks down as follows: the leading zero is ignored by CMS, the second digit "1" indicates a hospital facility, the third digit "2" specifies inpatient Part B services, and the fourth digit "1" signifies a single claim covering the full admission-to-discharge period. ^[1]

This code is distinct from standard inpatient Part A claims (code 0111) because it applies specifically when Medicare Part B only covers the inpatient stay—typically for beneficiaries who have exhausted their Part A benefits or are not eligible for Part A. The claim must include all services provided during the entire inpatient stay, from the date of admission through the date of discharge, on a single submission. ^[1]

Providers submitting code 0121 must ensure that all line-item charges reflect only Part B covered services, such as physician services, diagnostic tests, or certain medical equipment, rather than room and board or other Part A services. The UB-04 form must be completed with accurate patient demographics, admission and discharge dates, and revenue codes corresponding to the Part B services rendered. ^[2]

When to Use

Use code 0121 when a hospital provides inpatient care to a Medicare beneficiary who is covered only under Medicare Part B (not Part A) and the claim covers the entire inpatient stay from admission through discharge. This scenario commonly occurs when the beneficiary has exhausted their Part A inpatient days, is not eligible for Part A (e.g., certain ESRD patients), or has chosen not to use Part A benefits. ^[1]

This code is not appropriate for: (1) standard inpatient Part A claims (use 0111), (2) interim claims that require multiple submissions (use 0122, 0123, or 0124), (3) outpatient services (use 013X), or (4) late charge only claims (use 0125). Providers must verify that the entire stay is being billed in one submission; if the stay spans multiple billing periods or requires interim billing, a different frequency digit (2, 3, or 4) should be used instead. ^[1]

For MassHealth providers, the UB-04 form must be used for acute inpatient hospital claims when submitting paper claims (though electronic submission is required unless a waiver is obtained). The claim must include all required fields, including patient name, health insurance claim number, admission date, discharge date, and itemized charges for each revenue code. ^[2]

Step-by-Step Claim Example

Scenario: A 72-year-old Medicare beneficiary is admitted to General Hospital on January 10, 2025, for a three-day inpatient stay due to pneumonia. The patient has exhausted their Medicare Part A inpatient days for the benefit period but has active Part B coverage. The hospital provides Part B covered services including physician visits, respiratory therapy, and diagnostic lab work. The entire stay is billed on a single claim.

Step 1: Complete UB-04 Header Information

• Field 1: Provider name, address, and NPI
• Field 3a: Patient control number (e.g., 12345)
• Field 4: Type of Bill = 0121 (Hospital Inpatient, Part B only, Admit through Discharge)
• Field 6: Statement covers period: From 01/10/2025 to 01/12/2025
• Field 8a: Patient name
• Field 8b: Patient address
• Field 10: Patient date of birth and sex
• Field 11: Admission date = 01/10/2025
• Field 12: Admission hour = 14 (2:00 PM)
• Field 13: Admission type = 1 (Emergency)
• Field 14: Admission source = 4 (Physician referral)
• Field 15: Discharge hour = 10 (10:00 AM)
• Field 16: Discharge status = 01 (Discharged to home)

Step 2: Enter Revenue Codes and Charges (Field 42)

• Revenue Code 0010 (All-Inclusive Rate): $0.00 (not used for Part B)
• Revenue Code 0250 (Pharmacy): $150.00
• Revenue Code 0300 (Laboratory): $200.00
• Revenue Code 0420 (Physical Therapy): $100.00
• Revenue Code 0450 (Emergency Room): $0.00 (if applicable)
• Revenue Code 0510 (Clinic): $0.00
• Revenue Code 0762 (Respiratory Therapy): $175.00
• Total charges: $625.00

Step 3: Complete Remaining Fields

• Field 50: Payer identification (Medicare Part B)
• Field 51: Health insurance claim number (HICN)
• Field 52: Release of information certification
• Field 53: Assignment of benefits certification
• Field 54: Prior payments (if any)
• Field 55: Estimated amount due
• Field 56: NPI of billing provider
• Field 57: Other provider IDs
• Field 58: Insured's name
• Field 59: Patient's relationship to insured
• Field 60: Insured's unique ID
• Field 61: Group name
• Field 62: Insurance group number
• Field 63: Treatment authorization codes
• Field 64: Document control number
• Field 65: Employer name
• Field 66: Diagnosis codes (ICD-10-CM: J15.9 for pneumonia)
• Field 67: Procedure codes (if applicable)
• Field 68: Occurrence codes and dates
• Field 71: PPS code
• Field 72: External cause of injury code
• Field 74: Principal procedure code and date
• Field 76: Attending physician NPI
• Field 77: Operating physician NPI
• Field 78: Other physician NPIs
• Field 79: Other procedure codes
• Field 80: Remarks (if needed)

Step 4: Submit the Claim

• Submit electronically (preferred) or on paper if waiver approved
• Ensure all fields are complete and accurate
• Retain copy for records

Common Mistakes & Audit Red Flags

Mistake 1: Using code 0121 for Part A services. The third digit "2" indicates Part B only. If the claim includes room and board charges (revenue codes 0100-0199) or other Part A services, the claim will be denied or require correction. Always verify that only Part B covered services are billed under this code. ^[1]

Mistake 2: Submitting interim claims with frequency digit "1". Frequency digit "1" means the claim covers the entire stay from admission through discharge. If the stay requires multiple claims (e.g., due to billing system limitations or payer requirements), use frequency digits 2 (first interim), 3 (continuing), or 4 (last interim) instead. Using 0121 for an interim claim will result in a duplicate or incorrect claim. ^[1]

Mistake 3: Incorrect date ranges. The statement covers period (Field 6) must match the admission and discharge dates. If the dates are inconsistent or span beyond the actual stay, the claim may be rejected. For example, using 01/10/2025 to 01/15/2025 when the patient was discharged on 01/12/2025 would be a red flag. ^[2]

Audit Red Flags:

• High volume of 0121 claims from a single provider: May indicate systematic misuse or upcoding.
• Claims with revenue codes 0100-0199 (room and board): These are Part A services and should not appear on a Part B only claim.
• Claims with zero charges: Frequency digit "1" with zero charges may indicate a non-payment claim, which should use frequency digit "0" instead.
• Claims with discharge status codes indicating transfer to another facility: May require coordination with the receiving facility and could affect billing frequency.
• Claims with missing or invalid diagnosis codes: All diagnosis codes must be valid ICD-10-CM codes and support the medical necessity of Part B services.
• Claims with duplicate service dates: Multiple claims for the same admission date range may trigger a duplicate claim edit.

Related Codes/Fields

Code/Field	Description	Relationship to 0121
0111	Hospital Inpatient (Part A) - Admit through Discharge	Use for standard Part A inpatient stays; 0121 is for Part B only
0122	Hospital Inpatient (Part B only) - Interim First Claim	Use when the Part B stay requires multiple claims; 0121 is for single claim
0123	Hospital Inpatient (Part B only) - Interim Continuing Claim	Use for subsequent interim claims; 0121 is for single claim
0124	Hospital Inpatient (Part B only) - Interim Last Claim	Use for final interim claim; 0121 is for single claim
0125	Hospital Inpatient (Part B only) - Late Charge Only	Use to add charges after original claim; 0121 is for full stay
0131	Hospital Outpatient - Admit through Discharge	Use for outpatient services; 0121 is for inpatient Part B
Field 6 (Statement Covers Period)	Admission through discharge dates	Must match the dates for 0121 claims
Field 11 (Admission Date)	Date of inpatient admission	Required for 0121 claims
Field 16 (Discharge Status)	Patient discharge status code	Required for 0121 claims
Revenue Codes 0100-0199	Room and Board charges	Should NOT appear on 0121 claims (Part A services)
Revenue Codes 0250-0999	Ancillary Part B services	Appropriate for 0121 claims (e.g., lab, pharmacy, therapy)

^[1] | ^[2]

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References

[1] Noridian Bill Types — https://med.noridianmedicare.com/web/jea/topics/claim-submission/bill-types

[2] MassHealth UB-04 Guide — https://www.mass.gov/doc/ub-04-billing-guide-0/download