UB04 Patient's Relation to Insured Code 21: Unknown

Overview

Code 21 in UB-04 Form Locator 59 (Patient’s Relation to Insured) indicates that the patient’s relationship to the insured person is Unknown. This code is part of the standard relationship codes used on institutional claims to identify how the patient is connected to the primary insurance subscriber. According to Novitas Solutions, the complete list of valid codes for FL 59 includes: 01 (Spouse), 18 (Self), 19 (Child), 20 (Employee), 21 (Unknown), 39 (Organ Donor), 40 (Cadaver Donor), 53 (Life Partner), and G8 (Other Relationship) ^[1]. This code is typically used when the provider cannot determine the patient’s relationship to the insured, such as when the patient is unconscious, unaccompanied, or when documentation is incomplete.

When to Use

Code 21 should be used in FL 59 only when the patient’s relationship to the insured person is genuinely unknown and cannot be determined from available documentation or patient interview. Common scenarios include: (1) emergency department visits where the patient is unconscious or unable to communicate, (2) patients brought in by ambulance without identification or family members, (3) situations where the insurance card is present but the subscriber’s relationship to the patient is not clearly indicated, and (4) cases where the patient is a minor but the accompanying adult is not a legal guardian and cannot provide relationship information. Providers should make reasonable efforts to determine the correct relationship code before defaulting to 21. The MassHealth guide emphasizes that all fields must be completed accurately to avoid claim rejection or delay ^[2]. Using code 21 as a default when the relationship is actually known may result in claim denials or requests for additional documentation from payers.

Step-by-Step Claim Example

Consider a patient, Jane Doe, who is brought to the emergency department by ambulance after a car accident. She is unconscious and has no identification. Her insurance card is found in her wallet, listing “John Smith” as the subscriber, but no relationship is indicated. The provider cannot determine if Jane is John’s spouse, child, or other dependent. In this scenario:

1. Locate FL 59 on the UB-04 form (Field 59: Patient Relationship to Insured).
2. Enter code 21 in the two-character field.
3. Complete FL 58 (Insured’s Name) with “Smith, John” as shown on the insurance card.
4. Complete FL 60 (Insured’s Unique ID) with the subscriber ID from the card.
5. Submit the claim with all other required fields completed accurately.

The MassHealth guide notes that all fields must be completed correctly for electronic submission, as paper claims are no longer accepted without prior approval ^[2]. After submission, the payer may request additional documentation to verify the relationship, such as a police report or hospital admission records.

Common Mistakes & Audit Red Flags

Common mistakes when using code 21 include: (1) using it as a default when the relationship is actually known, which can trigger payer audits and claim denials; (2) failing to document the reason for using “Unknown” in the medical record, which may be requested during retrospective review; (3) using code 21 when the patient is clearly a spouse (code 01) or child (code 19) based on available information; and (4) leaving FL 59 blank instead of entering code 21 when the relationship is truly unknown. Audit red flags include: (a) frequent use of code 21 by a single provider, suggesting systemic failure to collect relationship information; (b) claims with code 21 that later have corrected codes after payment, indicating initial misrepresentation; and (c) use of code 21 for elective or scheduled services where relationship information should be obtainable. The MassHealth guide warns that incomplete or inaccurate fields may result in claim rejection or payment delays ^[2]. Providers should implement processes to verify patient-insured relationships at registration to minimize use of code 21.

Related Codes/Fields

Field/Code	Description	Source
FL 58	Insured’s Name (subscriber name)	[1]
FL 60	Insured’s Unique ID (subscriber ID number)	[1]
Code 01	Spouse	[1]
Code 18	Self	[1]
Code 19	Child	[1]
Code 20	Employee	[1]
Code 21	Unknown	[1]
Code 39	Organ Donor	[1]
Code 40	Cadaver Donor	[1]
Code 53	Life Partner	[1]
Code G8	Other Relationship	[1]

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References

[1] Novitas Solutions UB-04 Form Locator — https://www.novitas-solutions.com/webcenter/portal/MedicareJH/page9?articleId=123456

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