UB-04 / CMS-1450 Field Guide
UB-04 Form Locator 3a: Patient control number
The provider-assigned account/control number used to associate the claim with internal financial records.
Reviewed September 2026 · Educational reference — verify payer and program requirements.
What Form Locator 3a reports
The provider-assigned account/control number used to associate the claim with internal financial records.
What to check
- Use the current institutional claim instructions for the payer and bill type.
- Confirm the value matches the source record, provider enrollment, authorization or revenue-line detail that supports the claim.
- Do not substitute a narrative note when a designated code or identifier is required.
- Reconcile related form locators before filing.
Medicare reference: CMS publishes form locator completion guidance in Chapter 25 of the Medicare Claims Processing Manual. NUBC maintains the UB-04 data specifications and code sets used broadly across institutional billing.