What Is the PR-31 Denial Code?

Updated June 2026. CARC 31 is the standardized X12 code payers use to communicate one specific message: 'Patient cannot be identified as our insured.' The payer ran the patient's identifying information on your claim against its eligibility/membership file and could not find a matching active member.

Read that carefully, because it changes how you work the denial: the payer is not saying the service is non-covered, not medically necessary, or out of benefits. It is saying it cannot find the person. Until the patient is matched to a member record, the claim never reaches adjudication of the service itself.

PR-31 versus CO-31 is a group-code distinction:

• PR-31 pairs the reason code with the PR (Patient Responsibility) group code. Some payers use PR-31 to signal 'this is not our member, so any liability falls to the patient/guarantor to tell us who the correct payer is.' Despite the PR label, this is rarely a billable patient balance — see the patient-responsibility section below.
• CO-31 pairs it with the CO (Contractual Obligation) group code. This is more often seen when the payer treats the unmatched-member result as a provider-side write-off pending correction.

In both cases the underlying problem is identical: a mismatch between the identifiers on the claim and the identifiers in the payer's file. CARC 31 is informational about identity, not about the service. That is why the overwhelming majority of 31 denials are fixed with a corrected claim — not an appeal — once the right identifiers or the right payer are in place.

In our denial audits we typically see five root causes behind PR-31, in roughly descending order of frequency:

1. Wrong or transposed member ID. The single most common cause. A digit is dropped, transposed, or the alpha prefix is mistyped. Blue Cross/Blue Shield plans are especially sensitive — the three-character alpha prefix routes the claim to the correct Blue plan, and a wrong prefix produces a 'cannot identify' result even when the rest of the ID is correct.
2. Name or date-of-birth mismatch with the card. The payer matches on name + DOB + ID. A maiden name vs. married name, a nickname ('Bill' vs. 'William'), a hyphenated last name entered without the hyphen, or a DOB off by one digit all break the match.
3. Subscriber vs. dependent error. The patient is a dependent, but the claim was filed under the patient's own information instead of the subscriber's, or the relationship code (self/spouse/child) is wrong. Pediatric and spouse claims are the usual victims.
4. Claim sent to the wrong payer (or wrong payer ID). The patient changed plans, the front desk scanned an old card, the clearinghouse routed to a stale payer ID, or a Medicaid MCO claim went to fee-for-service Medicaid. The payer that received the claim genuinely has no record of this member — because the member belongs to a different payer.
5. Coverage inactive on the date of service. The member exists but was not active on the DOS — termination, a lapse in premium, a not-yet-effective new plan, or a retroactive eligibility change. Some payers return CARC 31 for this; others return CARC 27 (expenses after coverage terminated). When the patient is genuinely not active anywhere with this payer, the denial behaves like a coverage problem rather than a typo.

The practical takeaway: causes 1-3 are typos fixed by correcting your own data; cause 4 is a routing problem fixed by finding the real payer; cause 5 is a genuine eligibility problem that may require billing a different payer or the patient. Your first job on every PR-31 is to figure out which of the five you are looking at.

Work every PR-31 in this order. The goal is to identify which of the five root causes applies, then resubmit clean.

1. Pull the card image and the registration record. Compare the member ID, name spelling, date of birth, and group number on the claim against the actual insurance card on file. Most 31 denials die here — the typo is visible immediately.
2. Re-run real-time eligibility (270/271). Submit a fresh eligibility inquiry to the payer with the corrected identifiers. The 271 response confirms whether the member is found, active on the DOS, and which payer/plan is current. If the 271 comes back 'patient not found,' the identifiers are still wrong or this is the wrong payer.
3. Confirm the correct payer. If eligibility cannot find the patient, call the patient (or check a payer-discovery/insurance-discovery tool) to confirm the current carrier. Patients change jobs and plans constantly; the card you scanned may be six months stale. A claim sent to the wrong payer will never match no matter how clean your data is.
4. Verify subscriber and relationship. For dependents, confirm the claim is filed under the subscriber's ID with the correct relationship code (self/spouse/child) and the subscriber's name and DOB where the payer requires them.
5. Correct the identifiers and resubmit as a corrected claim. Update the member ID, name, DOB, payer ID, or subscriber data and resubmit. In most cases this is a corrected/replacement claim or a brand-new clean claim to the correct payer — not a formal appeal, because there is no adjudication decision to dispute, only an identity to fix.
6. If coverage was genuinely inactive on the DOS, the path changes: bill the correct active payer for that date, or — if there was no active coverage — move the balance to self-pay following your financial policy and, where applicable, your No Surprises Act good-faith-estimate obligations for uninsured patients.
7. Watch your timely-filing clock. A PR-31 does not pause timely filing. Every day spent re-verifying eats into the window with the correct payer, which may have a shorter limit. Work 31 denials fast and document the corrected-claim submission date.

Short answer: not yet — and usually not at all on the basis of the PR-31 alone.

Even though CARC 31 can arrive with the PR (Patient Responsibility) group code, a PR-31 is almost never a legitimate patient balance in the way a deductible or coinsurance is. The payer did not adjudicate the service and assign cost-sharing; it simply could not identify the patient. Billing the patient at this stage is premature and, in most scenarios, wrong:

• If the denial is a typo (causes 1-3): the patient is covered. The balance is yours to fix by correcting the claim. Balance-billing a covered patient for your own data-entry error is a contract violation with most payers and a reputational and compliance risk.
• If the claim went to the wrong payer (cause 4): the patient owes nothing yet; the correct payer has not been billed. You bill the right carrier first.
• If coverage was genuinely inactive on the DOS (cause 5) and no other payer covers it: now the patient/guarantor responsibility is real, but the cleaner basis for that balance is the eligibility/termination determination (often CARC 27 territory), handled through your self-pay and financial-policy process — including a good-faith estimate for uninsured patients under the No Surprises Act where it applies.

The disciplined rule: do not move a PR-31 to patient responsibility until you have (a) confirmed the correct payer, (b) confirmed coverage was inactive on the DOS for that patient, and (c) documented both. Until then, PR-31 is a data and routing problem the practice owns, not a bill the patient owes.

These three codes are constantly confused on denial worklists because they all touch eligibility. They are not the same, and the fix differs for each. Use this table to triage at a glance.

The core distinction: PR-27 means the member was real but their coverage ended — you are looking for a different active payer or a self-pay path. PR-31 / CO-31 means the payer never found the member at all — you are looking for a typo or the wrong payer. If you can re-verify the patient and find them active with this exact payer on the DOS, a 31 denial is almost certainly a data error you can correct and resubmit the same day. For deeper handling of the terminated-coverage path, see our PR-27 denial code guide.

CARC 31 frequently arrives with a Remittance Advice Remark Code (RARC) that tells you which identifier failed. The RARC is your fastest route to the root cause — read it before you start guessing. Common pairings:

If no RARC is present, default to the step-by-step work-down: card image first, then 270/271 eligibility, then payer confirmation. A blank-RARC 31 most often turns out to be a wrong member ID or a claim sent to the wrong payer.

How CARC 31 behaves varies by payer type, and the work-down shifts accordingly.

Commercial / Blue Cross Blue Shield. BCBS plans are the classic PR-31 generator because of the alpha prefix — the first three characters of the member ID that route the claim to the correct Blue plan. A wrong, missing, or transposed alpha prefix produces a 'cannot identify member' result even when the numeric ID is perfect. On any BCBS 31, verify the alpha prefix against the card first. Commercial payers generally accept a corrected claim with the fixed identifiers; no appeal is needed.

Medicare. With the move to the Medicare Beneficiary Identifier (MBI), a 31-type denial usually means the MBI is wrong, the patient is in a Medicare Advantage plan (so traditional Medicare has no record — bill the MA plan), or the patient is enrolled with a different MAC. Use the MBI lookup and the eligibility (HETS) response to confirm before resubmitting.

Medicaid and Medicaid MCOs. The most common Medicaid 31 cause is sending a managed-care member's claim to fee-for-service Medicaid (or to the wrong MCO). The state file shows the member is enrolled in an MCO, so FFS Medicaid cannot identify them. Confirm the patient's current MCO assignment in the state eligibility portal and route the claim to that MCO. Retroactive Medicaid eligibility changes also frequently surface as 31 or 27 denials.

Medicare Advantage / commercial replacement plans. When a patient moves from traditional Medicare or an old plan to an MA or replacement plan, claims to the old payer return 'member not found.' This is a routing problem — find the current plan via eligibility verification and rebill.

Across every payer type, the unifying discipline is the same: re-verify eligibility with a real-time 270/271 before resubmitting, so you confirm both the correct identifiers and the correct payer in one step.

PR-31 is one of the most preventable denials in the book because it originates almost entirely at the front desk. Working them reactively is pure waste; preventing them is a registration-quality project.

1. Run real-time eligibility (270/271) on every patient before the date of service — ideally at scheduling and again at check-in. The 271 response surfaces a wrong ID, an inactive plan, or a payer change before the claim is built, killing the denial at the source. This is the single highest-ROI control for 31 denials.
2. Scan the physical card every visit, not just at the first encounter. Patients change plans between visits without telling anyone. A scanned current card eliminates the stale-payer problem (cause 4).
3. Validate the member ID format and alpha prefix at point of entry. Build edits into your PM/registration system that flag obviously malformed IDs and missing BCBS alpha prefixes before the claim is submitted.
4. Standardize name and DOB capture. Train registration to enter the legal name exactly as printed on the card (no nicknames), capture maiden vs. married names where relevant, and double-key the date of birth. Most name/DOB mismatches are pure data-entry discipline.
5. Confirm subscriber vs. dependent and the relationship code for every dependent claim at registration, so pediatric and spouse claims file under the subscriber correctly the first time.
6. Track PR-31 root cause monthly. Categorize every 31 by which of the five causes it was. If wrong member IDs dominate, the fix is a registration edit; if wrong-payer dominates, the fix is mandatory card-scanning and eligibility at check-in. The denial mix tells you exactly which registration control to tighten.

In our experience, practices that run eligibility on 100% of scheduled patients and re-scan cards every visit cut CARC 31 volume sharply within a quarter — because the entire code exists to catch identity errors that a 271 response would have surfaced days earlier.

A practice running clean on PR-31 denials does four things consistently:

1. Eligibility is verified before the visit, every visit — not at billing time, when it is too late to prevent the denial. Real-time 270/271 at scheduling and check-in is the backbone.
2. The 31 worklist is triaged by root cause within 48 hours, because timely filing keeps running. Typos (causes 1-3) are corrected and resubmitted same-day; wrong-payer (cause 4) goes to insurance discovery; inactive-coverage (cause 5) goes to the self-pay/COB workflow.
3. Corrected claims, not appeals, are the default path. Teams waste hours writing appeal letters for a problem that has no adjudication to appeal. Correct the identifier, resubmit, move on.
4. The denial mix feeds registration training monthly, closing the loop between the back office (where the denial lands) and the front office (where the error was made).

Because PR-31 is fundamentally a registration and eligibility problem, the highest-leverage fix is upstream. If your front-desk and verification workflow cannot run eligibility on every patient and re-scan cards each visit, outsourced insurance eligibility verification services can own that step end to end, and denial management services can work down the existing 31 backlog while the prevention controls take hold. Either way, the metric to watch is the same: the share of claims that match the payer's member file on the first pass.