Introduction: Why COB Errors Are Surging
The painful reality is that payers are denying more claims than ever—and Coordination of Benefits (COB) stands near the top of the reasons list. In Experian Health’s State of Claims 2024 survey, 73 percent of front-office and billing staff said denials are on the rise, driven largely by missing or inaccurate information. MGMA polling adds that nine percent of all denials trace directly to COB disputes, putting them among the five most common rejection codes.
Why so many COB hang-ups? Today’s patients juggle employer plans, ACA exchanges, TRICARE supplements, Medicare Advantage, and Medicaid carve-outs. When a practice sends a claim to the wrong primary payer—or skips the secondary claim altogether—the result is predictable: delayed cash, frustrated patients, and double the back-office work.
The good news: you can wipe out most COB denials with a handful of process tweaks and smarter data automation. Below are the five pitfalls that trip practices up—and the playbook to sidestep each one.
Pitfall 1: Assuming the Patient Knows Which Plan Is Primary
Patients often guess at the order of benefits, but federal and commercial rules—not gut feelings—set the hierarchy. Medicare may suddenly become secondary if the patient is still employed at a large company; a child’s primary plan flips every January under the “birthday rule.” If registration staff rely solely on what patients tell them, the claim will likely hit payer code CO 22 (coverage terminated/other coverage).
Fix
- Run real-time eligibility (RTE) at check-in and again at every insurance change. Clearinghouses return an “other coverage” indicator that flags multiple active policies.
- Teach staff the three golden rules of primacy: the birthday rule for kids, the “larger employer” rule for Medicare members, and the “active coverage beats COBRA” rule for workers on continuation plans.
- Document the hierarchy in the EHR so that future visits default to the correct payer order.
Pitfall 2: Ignoring Payer COB Questionnaires and File Exchanges
Blue Cross, Aetna, and Cigna routinely pend claims until patients update their COB questionnaires. If your office tosses those questionnaires in the recycle bin—or never tells patients to complete them—the claim sits in limbo for 30 days, then flips to denial status.
Fix
- Watch your clearinghouse inbox. Most payers send “information requested” alerts electronically. Route these to a shared billing queue instead of an admin’s personal email.
- Trigger an automated text or portal alert asking the patient to complete the payer’s form online. A template like “Action needed from {Patient First Name}: Your insurer requires a quick benefits update to process last week’s visit” cuts turnaround times by half.
- Log the questionnaire submission date in the practice-management system so you can appeal if the payer still denies for COB.
Pitfall 3: Missing the Timely-Filing Deadline for Secondary Claims
Primary payment must land before you can bill the secondary, but that delay eats into the secondary plan’s timely-filing clock—often just 60 to 90 days from the original date of service, not the primary adjudication date. Practices that wait for paper EOBs or batch secondaries weekly risk automatic denials for “claim received after filing limit.”
Fix
- Enroll in ERA (Electronic Remittance Advice) and auto-post payments. An ERA can close within 24 hours of primary payment, freeing the secondary claim almost instantly.
- Configure your clearinghouse to “forward balance” so the secondary payer receives the primary EOB data in the same 837 transmission—no manual re-keying. CMS calls this a COB claim with “claims adjudication information.”
- Set an internal SLA: secondary claims must leave your system within two business days of primary payment.
Pitfall 4: Overlooking Duplicate Payments and Refund Obligations
When payer order is wrong, both plans may pay as primaries, leaving you with 200 percent reimbursement—and a compliance nightmare. If the practice spends the overage or bills the patient anyway, you risk payer audits, refunds with interest, or even exclusion from networks.
Fix
- Reconcile every ERA against expected payment. Many practice-management systems flag unexpected 100 percent or 0 percent balances.
- Route credit balances to a monthly refund review committee—even if that committee is just you and your office manager.
- Return overpayments within 60 days of identification to meet CMS’s “reverse false-claims” rule. Interest accrues after that.
- Send corrected claims to show the proper primary/secondary split, keeping your data clean for future visits.
Pitfall 5: Letting Manual Processes Choke the COB Workflow
The smaller the practice, the more likely COB tasks live in someone’s head—or on sticky notes. A sick-day or staff turnover can stall secondary billing for weeks, ballooning days-sales-outstanding (DSO) and frustrating patients who suddenly get balance bills.
Fix
- Automate wherever your system allows. Map EDI “COB loops” so secondary claims file automatically once primary payment posts.
- Create a daily COB worklist. The list should spell out unfinished tasks: questionnaires pending, secondary claims in draft, credit balances awaiting refund.
- Cross-train at least one backup on COB essentials—verifying payer order, forwarding balances, appealing CO 22 denials.
Track KPIs that expose COB delays:
- Average days between primary adjudication and secondary submission (target < 2 days).
- Number of claims denied for CO 22 or CO 23 each week (target < 1 percent of claims).
- Dollar amount of credit balances older than 30 days awaiting refund.
Building a COB-First Culture: Seven High-Impact Habits
- Embed insurance discovery in every intake. Third-party tools can scan clearinghouse history and flag other active coverage before the visit.
- Run a “COB huddle” on Monday mornings. Review the prior week’s CO 22 denials, questionnaire requests, and credit-balance list.
- Turn the front desk into COB educators. Give staff a one-page script that explains primary vs. secondary insurance. Patients who understand the rules complete questionnaires faster.
- Store insurance cards—both sides—in the EHR. Many secondary payers want the primary’s BIN, PCN, and group numbers.
- Tie staff bonuses to denial reduction. When employees see a financial upside, questionnaire follow-up suddenly becomes urgent.
- Leverage payer portals for same-day questionnaire status. BCBS and Aetna post COB questionnaire completion in real time.
- Audit five random COB claims a month. Look for correct payer order, timely filing, and zero residual balances. Use findings for micro-training.
Quick Guide: Appealing a CO 22 Denial in 48 Hours
- Verify coverage order through RTE or payer portal.
- Gather proof: COB questionnaire date stamp, primary EOB, patient statement of coverage.
- Submit corrected claim (frequency code 7) with the proper primary/secondary details in the 2320 loop of the 837.
- Attach primary EOB electronically or fax it with the payer-specific COB cover sheet.
- Track the appeal in a denial-management queue and follow up at 14-day intervals until adjudication.
Measuring Success: From Denial-Prone to Denial-Proof
Practices that implement these COB safeguards typically see:
- CO 22/CO 23 denials drop below one percent within 60 days.
- Secondary-claim charge lag shrink from 10 days to under 48 hours.
- DSO reduce by four to seven days, injecting welcome cash flow without adding staff.
- Credit-balance backlog cleared each month, slashing audit risk and boosting patient satisfaction scores.
Conclusion: Put COB on Autopilot and Get Back to Patient Care
Coordination of Benefits will always be a moving target—patients change jobs, divorce, or age into Medicare every day. But the revenue damage isn’t inevitable. By verifying payer order up front, responding instantly to questionnaires, firing secondary claims inside 48 hours, reconciling overpayments, and automating every step you can, your practice will turn COB chaos into a routine back-office chore.
Remember: every CO 22 denial you prevent is one less phone call, one less appeal packet, and one more day your staff can focus on higher-value tasks like prior authorizations and patient collections. Master these five pitfalls, and COB will transform from a chronic headache into an afterthought—just another clean claim on its way to payment.
