Third-party liability

Editorial approval scope: The team checked current source fidelity, scope boundaries, dates, arithmetic, reader usefulness, practical workflow, and general-information limitations.

TPL identifies liability; COB applies the sequence

The Medicaid Coordination of Benefits and Third Party Liability page defines TPL as a third party's legal obligation to pay part or all medical-assistance expenditures. It describes coordination of benefits, or COB, as the activity of determining Medicaid benefits when another person, entity, insurer, or program may be liable.

The HealthCare.gov glossary offers related definitions for coverage, coordination of benefits, claims, networks, and appeals. In operational terms:

• TPL asks who has a legal payment obligation.
• COB identifies the order and effect of multiple coverage sources.
• Recovery seeks repayment after a responsible program or plan already paid.

A payer labeled “primary” still needs service-specific coverage and claim evidence. A secondary payer may owe nothing after applying its own rules.

A third party can take several forms

Medicaid lists possible liable resources such as group health plans, self-insured plans, managed care organizations, pharmacy benefit managers, Medicare, court-ordered coverage, liability settlements, workers' compensation, long-term-care insurance, and other coverage programs unless law excludes them.

These sources do not all behave like ordinary health insurance. An automobile or liability claim may depend on an accident investigation or settlement. Workers' compensation depends on work-related injury rules. A third-party administrator may supply data or process claims while another entity holds financial liability. Store the actual legal or contractual role rather than inferring it from a company name.

Medicaid is generally the payer of last resort

The Medicaid overview states that other available third-party resources must meet their legal obligations before Medicaid pays and that states must take reasonable measures to identify liable parties. Current 42 CFR 433.136 supplies federal Medicaid TPL definitions.

The general last-resort principle has service- and rule-specific procedures and exceptions. Current 42 CFR 433.139 addresses payment when third-party liability exists. A June 2025 Medicaid FAQ illustrates that cost avoidance generally applies when probable TPL exists, while specified pediatric preventive and medical-support situations use a pay-and-chase route.

That FAQ concerns a defined school-based question and federal Medicaid requirements. It does not create one billing sequence for every ABA service, state plan, waiver, managed-care organization, or third party. Use the current state or MCO provider source and preserve its effective date.

Build a payer-order record before claim release

For each member-service-date configuration, record:

• every possible coverage or liable-party source and why it may apply
• member, policy, claim, accident, court-order, or workers' compensation identifiers as applicable
• effective dates, service coverage, network, provider, location, and authorization states
• payer-order decision, source, state rule, managed-care contract or guide, and effective date
• primary claim route, filing deadline, submission proof, status, EOB or remittance, and denial reason
• secondary claim route, required crossover or attachment, filing deadline, status, and payment
• member billing protection, estimate, payment, refund, recovery, appeal, and open issue
• owner, next action, due date, escalation, and final disposition

Update other-insurance information at intake, renewal, reported coverage change, accident, new court order, employment change, and payer discovery. A historical payer response may become stale even while Medicaid eligibility remains active.

Preserve the primary payer's business meaning

Track whether the primary source paid, denied as noncovered, rejected for a correctable transaction defect, requested information, remained pending, reversed, or reprocessed. A clearinghouse acceptance does not establish payer adjudication. A generic denial screenshot may lack the member, service date, claim number, or reason needed for a secondary submission.

Submit to the secondary route only when its requirements are met. Some systems cross claims automatically; others require a provider submission, EOB, remittance, denial detail, or specific adjustment code. Record which process applies rather than assuming a crossover occurred.

TPL information should guide payment sequencing without changing clinical authorship. Staff should never revise a service record to match a payer-order assumption or describe a primary denial as evidence that the service lacked clinical value.

Protect the family from an unsupported balance

Before billing a family, reconcile primary and secondary adjudication, contractual write-offs, Medicaid rules, cost-sharing protections, previous collections, refunds, and any recovery action. A pending TPL investigation is not permission to transfer an uncertain balance to the client.

Dual Medicare and Medicaid coverage requires additional care. The current CMS Qualified Medicare Beneficiary page states that federal law prohibits Medicare providers and suppliers from billing QMB individuals for Medicare Part A or Part B cost sharing on Medicare-covered items and services. Verify the member's exact status, service, provider obligations, and current guidance.

Immediate safety care, mandated reporting, and emergency action follow their own legal and clinical routes. An administrative TPL question should not delay required emergency response.

A fictional TPL worklist

A fictional child has Medicaid and an employer-sponsored plan that the current state source identifies as primary for the ABA service. Ten claims reach the worklist's defined review date. The practice submits all ten through the documented primary route.

The primary plan pays seven, issues final noncoverage denials for two, and leaves one pending for missing coordination information. Primary-disposition completeness is 9 of 10, or 90%. The pending claim stays in the denominator with an owner and age.

Under the fictional state and MCO rules, eight of the nine finalized claims have the required evidence and provider configuration for secondary release. One paid primary claim is held because the Medicaid location record is unresolved. Secondary-release readiness is 8 of 9 finalized claims, or 88.9%, while original-worklist-to-secondary-release yield is 8 of 10, or 80%.

These rates measure workflow states. They do not establish Medicaid payment, final member responsibility, or the correctness of the primary decision. The practice keeps each primary remittance or denial, secondary submission proof, adjustment, recovery, and family-ledger action linked to the original claim.

Measure mature, scoped cohorts

Useful measures include payer-order decisions completed divided by configurations due, primary dispositions matched divided by mature primary claims, and secondary submissions released with required evidence divided by finalized claims eligible under the named route. Report unresolved claims, recovery notices, and family balances by count and age.

Audit repeated errors by state, MCO, liable-party type, product, service, denial, and workflow version. Common causes include stale other insurance, wrong order, incomplete primary evidence, missed crossover, unresolved accident status, and secondary timely-filing loss.