CMS-1500 Item 23: Authorization, Referral, and CLIA Numbers

Item 23 is often labeled “prior authorization number,” which makes it sound narrower than it is. The current NUCC instruction manual lists a payer-assigned prior authorization number, referral number, mammography certification number, or Clinical Laboratory Improvement Amendments (CLIA) number for the current service. CMS's Medicare training also treats it as situational and says to use the appropriate 837P Loop 2300 REF for the value being reported. The first step is not to paste the number into a box: identify what kind of number it is, who issued it, and whether the payer requires it on this claim.

These values are not interchangeable just because a billing system places them in the same interface. An authorization reference is not a referral number, and neither is a CLIA certification number. CMS says Item 23 can contain only one condition on the Medicare paper claim; if another condition applies, report it on a separate CMS-1500 claim. Its 837P training likewise says to choose the appropriate 2300 REF based on the value. Other payers may publish their own claim-edit or companion-guide details, so use their current instructions for commercial and Medicaid claims.

A practical example shows why the distinction matters. A diagnostic lab may have a payer referral or prior approval tied to the patient's episode, while the test site separately holds a CLIA certificate. Those records answer different questions: one documents the payer's utilization or referral requirement; the other identifies the laboratory certification relevant to testing. The billing office should not replace a missing payer approval with the laboratory's CLIA number simply because both can be associated with Box 23. Verify which condition the payer asks the claim to report and use the source record for that identifier.

A number copied from a portal is not enough to establish that an authorization covers the claim in front of you. Compare the approved member, billing or rendering provider as applicable, service or procedure, place of service, date range, and authorized units or visits with the actual encounter. Check whether the payer expects one number per claim, line, episode, or authorization record. If the service changed after approval—for example, the date moved, the location changed, or the ordered item was different—ask the payer or follow the organization's documented process to find out whether an update is required. Do not infer coverage from a number that simply looks valid.

Authorization and payment adjudication are separate steps. An approval does not by itself guarantee payment for every later claim. The member still must have applicable coverage, the service must match the approval and policy, the provider must meet participation and enrollment requirements where relevant, and the claim must satisfy billing and coding rules. That is why the person who enters Item 23 should preserve the approval details and source, not just the identifier string.

Not every number associated with a claim belongs in Item 23. For example, NUCC assigns corrected or replacement claim reference details to Item 22, not Item 23. A member ID belongs in the insured field; an NPI belongs in the appropriate provider field; and a local account number or internal tracking ID should not be presented as a payer authorization. Sending the wrong kind of value can pass a superficial format check and still fail payer matching. Use the claim form instructions and the payer companion guide to identify the field's semantic purpose before entering the value.

For electronic professional claims, the 837P carries claim-level reference information in Loop 2300 REF segments. The segment qualifier identifies what type of reference follows; the value alone does not communicate whether it is an authorization, referral, or another identifier. CMS's training explicitly tells submitters to use the appropriate 2300 REF according to the value being reported. In an EHR or practice-management system, a field called “authorization number” may populate a specific REF qualifier behind the scenes. Ask the billing lead or clearinghouse support to confirm the mapping if an edit names the segment or the value is not appearing as expected. Do not move a number to a different REF type merely because the text of a rejection sounds similar.

The NUCC 2025 manual describes a 29-character field and says not to include hyphens or spaces within the Item 23 number. Those are form-level instructions. Your payer's electronic companion guide or portal may impose additional formatting, placement, or matching rules. Do not shorten a long identifier, add punctuation, or remove characters based on guesswork; compare it with the source record and follow the payer's stated format. When a system automatically strips punctuation, confirm that the underlying value remains identifiable in the billing record and any required supporting documentation.

When a payer says an authorization is missing or invalid, separate data errors from coverage or policy decisions. Confirm the claim was sent to the intended payer and correct member. Check whether the service required authorization on the date of service, whether the approval applied to this provider and setting, and whether the number is in the correct paper field or electronic REF segment. Compare every character against the payer record, then look for a date, code, unit, or location mismatch. If the payer record is correct but the claim mapping is wrong, involve the billing-system owner or clearinghouse. If the service was never approved, a biller must not manufacture a number; route the case to the authorized team and follow the payer's correction or appeal process.

The prior-authorization workflow guide covers how teams request approval, track the decision, and hand it to scheduling and billing. This article focuses on the final claim-field decision. The distinction matters: a team can complete the authorization request correctly but lose the handoff before the claim is submitted. Build a workflow that stores the payer's original decision, its effective dates and scope, and the claim-system field or 837P mapping. At charge review, compare the actual encounter with that record. If the values disagree, pause submission and resolve the difference through the payer or designated internal owner.

A referral also should not be confused with proof of active coverage or an eligibility response. A plan may ask for a referral identifier even when a separate authorization is not required, and one approval does not necessarily satisfy another plan's referral rule. At scheduling, record the exact payer product and source checked; at charge entry, retrieve the referral or authorization tied to that member and service. If a patient changes plans or the service moves to a different location, repeat the payer-specific check instead of carrying an old number forward automatically.

Use Item 23 only when the relevant condition applies. The national form manual, CMS Medicare training, and a payer's companion instructions should be read together, with the payer's rule governing its own claim edits. If an instruction is ambiguous, ask the payer or the organization's billing lead before changing production data. A precise field entry is useful only when the underlying approval or identifier is real and actually belongs to the service being billed.