Did you know that, according to the National Library of Medicine, medical debt worth $194 billion was in active collection in 2024?
Rising medical care costs and the strain on lower-income households remain a consistent reason for this. Medical insurance payers cater to millions of individuals through primary and secondary insurance.
However, incorrect payer sequencing is a common and costly cause of claim denials. Submitting a claim to the wrong payer first not only delays payment, but it can also trigger several corrective measures:
- Resubmission
- Corrected claims
- Delayed reimbursement
These corrective measures increase accounts receivable (A/R) balance, which strains cash flow. Similarly, if service providers handle high claim volumes, even a single coordination of benefits (COB) error results in weeks of delayed payment.
To avoid such circumstances, billing teams must understand how primary and secondary insurance work from a billing perspective. So, let’s begin.
What is Primary Insurance?
Primary insurance coverage in medical billing refers to the payer who pays and adjudicates the claim first. Typically, the payer in primary billing:
- Processes the claim according to its fee schedule.
- Applies the patient’s deductibles, such as coinsurance and copays.
- Issues an Explanation of Benefits (EOB) detailing what was paid and what remains unpaid.
Therefore, each submitted claim must be billed to the primary payer before any other insurance applies. In such cases, the primary payer’s EOB acts as the basis of any subsequent secondary claim. In other words, if there is no primary insurance, secondary billing may not be possible.
What is Secondary Insurance?
Secondary insurance is applied to a claim only after the primary payer completes their adjudication. Generally, the secondary payer may cover some or all of the remaining balance, which involves:
- Deductibles
- Coinsurance
- Copays
However, the secondary insurance coverage is applicable only up to its coverage limits. Typically, a secondary payer may require the primary payer’s EOB. If the claim is submitted electronically, COB information is typically transmitted on the electronic 837 claim using the appropriate COB segments.
Similarly, if the required primary adjudication information is missing, the secondary payer may reject or deny the claim, depending on its policies.
Primary vs. Secondary Insurance: Key Differences
Understanding the differences between primary and secondary insurance is imperative for billing professionals who wish to avoid claim submission errors. From a workflow standpoint, the two payers may differ because of the following factors:
| Primary Insurance | Secondary Insurance | |
|---|---|---|
| Claim Submission Sequence | Billed right after the service and first in sequence. | Billed for the remaining amount once the primary EOB is received. |
| Adjudication Process | Applies full fee schedule, deductible, copay/coinsurance. | Applies its policy to the remaining balance of the primary payer. |
| EOB Requirement | Generates the initial EOB. | Requires the initial EOB for adjudication. |
| Reimbursement Responsibility | Pays first, up to plan limits. | Pays the remaining balance, up to its own limits. |
| COB Dependency | Determines payer order for all downstream billing. | Fully dependent on accurate primary designation. |
| Common Billing Pitfall | Incorrect primary payer designation. | Claim submitted without primary EOB attached. |
Primary and Secondary Insurance Rules
The payer order for primary and secondary insurance is not random. Typically, it is determined using coordination of benefits (COB) rules, which are commonly based on the NAIC Model COB Regulation. However, it is essential to note that payer contracts and government programs may follow additional rules.
Conversely, for Medicare, the federal Medicare Secondary Payer (MSP) provisions may be used. The most essential rules that may apply include:
Employment-Based Coverage Rule
If an individual has coverage as an employee under one plan and as a dependent under another, the employee’s own group health plan is generally primary.
Birthday Rule
If a dependent child has coverage under both parents’ plans, the parent whose birthday (month/day) falls earlier within the calendar year holds the primary insurance policy.
Medicare Secondary Payer Rules
Spouses and workers (65 years and older), with a group health plan from an employer with 20 or more employees, may have different rules applicable. For such individuals, the employer plan is generally primary, and Medicare is secondary.
Conversely, for small employers, Medicare is typically the primary payer, and the employer group health plan is typically the secondary payer.
Medicaid as the Last Payer
According to policy, Medicaid is generally the payer of last resort after all other available coverage limits are exhausted. If medical billers miss this sequence and bill Medicaid first, the claim will be denied.
Active vs. Retired Status
Active employee group coverage is generally considered the primary payer over retiree coverage or Consolidated Omnibus Budget Reconciliation Act (COBRA) continuation coverage for the same individual. However, since the payer order is vital, the billing staff should verify:
- Dependent relationships during intake
- Employment status
- Employer size
How Does Primary and Secondary Insurance Work?
Before handling claims involving primary and secondary insurance, billers must understand how the insurance works. It is a step-by-step process designed to bill multiple payers in the correct order.
- The process begins by determining the primary and secondary insurance payer according to Coordination of Benefits (COB) rules.
- According to the COB rules, the billing team knows which payer is liable to pay first for patients with multiple coverages.
- Once the billing team establishes the payer order, the remaining process moves in a fixed sequence.
- The claim is first submitted to the primary payer, who adjudicates it according to its fee schedule and the patient’s benefits. Then the patient’s plan-specific deductible may also be applied to the claim.
- If the patient’s annual deductible has not been exhausted, allowed charges are applied toward the deductible. This is typically done before any payments are made, so the secondary payer calculates the remaining patient responsibility.
- Once the primary payer adjudicates the claim, an EOB is generated. This EOB includes the amount allowed and paid, as well as patient responsibility.
- This EOB is submitted along with the claim to the secondary payer.
- In the next step, the secondary payer processes the remaining balance according to its own benefits and rules of COB, and typically does not pay beyond the remaining allowable amount.
- However, the secondary payer must not cover 100% of the balance. Instead, the payment amount is determined by the secondary payer’s benefit structure.
- Any remaining balance after both payers have processed the claim may become the patient’s responsibility.
Important Billing Insight: The typical billing process for primary and secondary insurance involves the steps discussed above. However, the reimbursement may vary depending on payer contracts, benefit design, and contractual adjustments. Therefore, billing teams must always verify the details.
How is Primary and Secondary Insurance Determined?
Determining primary and secondary insurance for any claim may initially be a complicated decision. However, the payer sequencing begins during registration, even before most new billers generate the claim.
To reduce complications, billing and front-office staff must use the following best practices:
Insurance Card Collection
The insurance cards of all active health plans should be collected at every patient visit. Since the primary and secondary insurance may be subject to change, front-desk staff should verify eligibility before each encounter. Remember, relying on information from past visits may lead to rejected claims.
Real-Time Eligibility Verification
The insurance eligibility should always be reviewed and verified before services are provided. This can be done by verifying eligibility through the payer portal, clearinghouse, or other eligibility verification tools. Ideally, the staff should verify the following before rendering services and billing the payer:
- Correct payer order
- Plan details
- Coverage status
- Member eligibility
COB Patient Interview
When a patient is registered, they should be questioned regarding the Coordination of Benefits (COB). Similarly, the staff should question patients regarding their:
- Dependent status
- Spousal coverage
- Employment status
- Medicare or Medicaid enrollment
- Employer size
With this information, the billing team can determine the primary and secondary insurance payer in the correct sequence.
Payer COB Validation
Accurate COB information is necessary for proper claim processing. Therefore, the patient’s insurance information should be verified with the payer’s Coordination of Benefits records. It is necessary to note that several commercial insurers and Medicare maintain COB data.
However, these records may not reflect new changes in the coverage, which is why patient confirmation is required during the verification process.
COB Documentation
The Coordination of Benefits information should be recorded once it is verified. Therefore, it should be added to the patient’s account or practice management system. Proper COB documentation helps ensure claims are submitted to the correct payer in the right sequence. It also avoids duplicate verification efforts and ensures the claims are processed in the right sequence.
Discrepancy Resolution
If the billing staff encounters inconsistencies between patient-provided information and payer-reported COB data, these should be resolved before claim submission. Resolving discrepancies in primary and secondary insurance ensures reduced:
- Claim denials
- Payment delays
- Unnecessary rework throughout the revenue cycle
To determine primary and secondary insurance smoothly, the billing staff must verify the COB proactively. It should be completed before claim submission to maintain accurate payer sequencing and avoid unnecessary denials.
Common Examples of Primary and Secondary Insurance
Although we have discussed almost everything regarding primary and secondary insurance, there’s more. Understanding common billing scenarios is one of the easiest ways to understand how primary and secondary insurance work.
Here’s how billing should work if:
- A patient has Medicaid and another health plan. Bill the other health insurance first, then Medicaid.
- A patient gets injured in an auto accident and has both auto liability and health insurance. Bill the auto liability insurance first, then the health insurance.
- A retired patient has both Medicare and retiree health coverage. Bill Medicare first, then the retiree health plan.
- A child is covered under both parents’ health plans. Bill that parent’s insurance plan first, which is considered primary under the birthday rule, followed by the other parent’s plan.
- A patient is covered by both their employer’s health plan and their spouse’s employer plan. Bill the patient’s employer plan first, followed by the spouse’s employer plan.
- A patient who is 65+ is actively employed by a large employer and also has Medicare. Bill the employer group health plan first, then Medicare.
Summary
Accurately identifying and billing the primary and secondary insurance directly impacts revenue cycle performance. When billers sequence the claims correctly, they increase the first-pass claim acceptance and accelerate reimbursement timelines. Additionally, it reduces denials and costly rework, keeping A/R days under control.
If payer sequencing errors are eating into your reimbursement timelines, consider MediBillMD’s medical billing services for correctly submitted claims.
FAQs
- Is Medicare always primary insurance?
No. Medicare’s ‘primary payer’ status depends on factors like employment status and employer size. Therefore, Medicare may act as the primary or secondary payer depending on the patient’s specific coverage situation.
- Is Medicaid primary or secondary insurance?
Medicaid is always considered a secondary payer. Typically, it is the payer of last resort and can be charged only after all other applicable coverages are exhausted.
- Are providers required to bill secondary insurance?
Providers are expected to charge secondary coverage to minimize patient financial responsibility. However, the specific obligations can vary by payer contract and state regulations.
- Can you bill secondary insurance if the primary is denied?
Yes, the secondary payer can still be billed if the primary is denied. However, the bill should also include the primary payer’s denial EOB. However, specific balance coverage depends on the secondary plan’s specific rules and the reason for claim denial.
- Can you bill secondary insurance without billing primary?
No, secondary insurance can only be billed after the primary payer has been billed and an EOB has been issued as proof of claim adjudication. Skipping the primary payer can result in denial for missing COB information.
