When Medicare and another payer may both be responsible for a claim, coordination-of-benefits rules determine which payer is primary and which is secondary. Medicare’s current “Who pays first?” tool asks about the type of other coverage, age, employment status, employer size and other circumstances.

If the wrong payer is billed first, an otherwise covered infusion or injection can deny or sit unpaid until the coordination record is corrected.

Questions to answer before the next call or submission
  • List every active medical payer.
  • Identify whether employer coverage is based on current or former employment.
  • Use Medicare’s “Who pays first?” tool for the current situation.
  • Make sure the treatment site has the correct primary and secondary payer order.
  • Confirm authorization requirements for each payer that requires them.
  • If a claim denies for payer order, correct coordination before filing a medical-necessity appeal.

Current employment and retiree coverage are not the same thing

For Medicare beneficiaries with employer coverage, who pays first can depend on whether the coverage is based on current employment and on employer size. Retiree coverage and COBRA often coordinate differently.

Do not infer the payer order from the insurance-card order in a wallet. Use Medicare’s current tool or the Benefits Coordination & Recovery Center when needed.

Secondary does not mean “pays everything Medicare leaves behind”

The secondary payer pays only according to its own coverage rules. A remaining balance can still exist if the secondary plan does not cover the service, has its own cost sharing, or requires a network or authorization rule.

Update coordination information before a high-cost claim if possible

Tell the treatment site about all active coverage. If employment or insurance recently changed, confirm that Medicare’s coordination record is current before a large Part B claim is submitted.

Use the source that actually controls your case

MedicineCostHelp can organize the problem, but the member-specific plan, Medicare program, provider billing record or assistance program makes the actual decision. Save written determinations and reference numbers so the next person does not have to reconstruct the case from scratch.

Official sources

Medicare — Who pays first? →Medicare — How Medicare works with other insurance →