UB04 Patient Sex Code M: Male

Overview

Field 11 (Patient Sex) on the UB-04 (Form CMS‑1450) is used to capture the sex of the patient. The field is defined as a one‑character alphanumeric code (AN 1) and is part of the standard UB‑04 layout maintained by the National Uniform Billing Committee (NUBC). According to the Medicare Claims Processing Manual, Chapter 25, the NUBC maintains “lists of approved coding for the form” and Medicare Administrative Contractors “must be able to capture all NUBC‑approved input data” ^[1]. The MassHealth UB‑04 Billing Guide also references “Code Sets for the UB‑04 Claim Form” as the authoritative source for permitted values in each field ^[2].

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When to Use

Use code M in Field 11 whenever the patient’s legal sex recorded in the medical record or eligibility system is male. The code is required on all institutional claims (inpatient, outpatient, and other) submitted on the UB‑04 or its electronic equivalent (837I). Both the CMS chapter and the MassHealth guide emphasize that the form serves “multiple third‑party payers” and that “a particular payer may not need some data elements” ^[1]. However, when the field is populated, only NUBC‑approved codes may be used. Therefore, code M must be used for male patients to ensure correct processing and to avoid rejections or requests for correction.

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Step‑by‑Step Claim Example

This example shows how to complete Field 11 on a UB‑04 paper claim for a male patient.

1. Locate Field 11 – On the UB‑04 form, Field 11 is the “Patient Sex” box located between the patient birthdate (Field 10) and the admission/start of care date (Field 12). The field has a single‑character width.
2. Verify patient sex – Confirm the patient’s legal sex from the registration system or eligibility file. For a male patient, the appropriate code is M.
3. Enter the code – Write the capital letter M clearly in the field. Do not use periods, spaces, or any other characters.
4. Complete the rest of the claim – For a standard inpatient stay, Fields 1‑10, 12‑15, and subsequent fields must be filled per payer instructions. For MassHealth, refer to the “How to Complete the UB‑04 Claim Form” section of the guide ^[2].
5. Submit the claim – For Medicare, send the form to the appropriate A/B MAC (A) or (HHH).

Step	Action	Field 11 Detail
1	Locate FL11	Upper‑left section after birthdate
2	Check patient sex	Male
3	Enter code	M
4	Finalize fields	Ensure no stray marks in field
5	Submit	Follow Medicare or MassHealth routing rules

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Common Mistakes & Audit Red Flags

• Using the wrong code – Never use “Male” spelled out or “MALE” in the field; the one‑character code is required.
• Omitting the field – Leaving Field 11 blank may cause a payer to reject the claim or request a corrected form.
• Typographical errors – Illegible handwriting or printing “M” too close to the field’s border can be misread. Use a clear, uppercase letter.
• Data mismatch – If the sex code in Field 11 does not match the sex recorded in the patient’s insurance eligibility or in other claim fields (e.g., condition code for sex‑specific procedure), it may trigger a medical review or audit for potential fraud or abuse.
• Payer‑specific variations – While the base code set is NUBC, some payers (e.g., managed care plans) may have additional requirements. Review the payer’s billing instructions before submission. The CMS manual notes that “a particular payer may not need some data elements” ^[1], but if the field is required, only the correct NUBC code is acceptable.

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Related Codes/Fields

The following table lists adjacent fields and related codes on the UB‑04 that interact with Field 11.

| Field | Name | Description | Code Relevance | |-------|------|-------------|----------------| | FL10 | Patient Birthdate | Patient’s date of birth (MMDDCCYY) | Used with sex for patient identification | | FL11 | Patient Sex | M = Male (as defined by NUBC) | Primary focus | | FL12 | Admission/Start of Care Date | First day of service or admission | Not sex‑dependent | | FL14 | Priority (Type) of Admission or Visit | Emergency, urgent, elective, etc. | ---END---

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References

[1] CMS Chapter 25, §70.1 — https://www.cms.gov/regulations-and-guidance/guidance/manuals/downloads/clm104c25.pdf

[2] MassHealth UB‑04 Guide, p. 23 — https://www.mass.gov/doc/ub-04-billing-guide-0/download