What is a timely filing limit?

The deadline by which a payer must receive the initial claim, measured from the date of service. It ranges from 90 days to 365 depending on the plan, and a claim filed late is almost never payable or appealable.

How is Medicare Advantage different from traditional Medicare?

Medicare Advantage plans are administered by commercial insurers under their own networks, authorization rules, and appeal processes. They must cover what Medicare covers, but the operational rules follow the commercial plan, not the MAC.

How do I bill secondary insurance?

Submit to the primary payer first, then file the secondary claim with the primary remittance attached, ensuring the coordination-of-benefits amounts match the primary's adjudication exactly. Mismatched COB fields are the most common secondary denial.

Do workers' compensation claims follow the same rules?

No. Workers' comp uses state-specific fee schedules, separate forms and authorization processes, and often paper submission. Timely filing and appeal rights are set by state statute rather than by contract.

What should I do when a payer underpays a contracted rate?

Compare the paid amount to the contracted fee schedule, document the variance, and file a formal underpayment appeal citing the contract. Systematic underpayments are worth auditing in bulk rather than claim by claim.

Payers

Payer Rules: Medicare, Medicaid and Commercial Plans

The same claim, twenty-seven different rule books.

Every payer adjudicates the same CPT code against a different policy set. Timely filing windows range from 90 days to a full year. Some plans require authorization for an imaging study that another pays without question. Modifier acceptance, place-of-service rules, and secondary claim handling all vary, and the variation is not published in one place.

That is the reason this section exists. Rather than a single generic 'insurance billing' page, we maintain a directory of individual payers with the rules that actually affect claims — filing deadlines, appeal levels and addresses, prior authorization requirements, portal capabilities, and the denial codes each one issues most often.

Above the directory sit the structural topics: how Medicare Parts A, B, C, and D differ for a billing office, why Medicare Advantage plans behave like commercial plans despite the name, how state Medicaid programs and managed care organizations diverge, and how workers' compensation and auto liability claims follow entirely separate fee schedules and forms.

Compliance belongs here too. HIPAA, the No Surprises Act, payer audits, RAC and TPE reviews, and documentation retention are all payer-facing obligations, and getting them wrong is more expensive than any single denial.

Explore this section

Medicare
Parts A through D, MACs, LCDs, ABNs, and Medicare Advantage.
Medicaid
State programs, managed care organizations, and dual-eligible claims.
Commercial Payers
BCBS, UnitedHealthcare, Aetna, Cigna, Humana and regional plans.
Workers' Comp & Auto
State fee schedules, adjusters, liens, and no-fault auto claims.

Frequently asked questions

What is a timely filing limit?: The deadline by which a payer must receive the initial claim, measured from the date of service. It ranges from 90 days to 365 depending on the plan, and a claim filed late is almost never payable or appealable.
How is Medicare Advantage different from traditional Medicare?: Medicare Advantage plans are administered by commercial insurers under their own networks, authorization rules, and appeal processes. They must cover what Medicare covers, but the operational rules follow the commercial plan, not the MAC.
How do I bill secondary insurance?: Submit to the primary payer first, then file the secondary claim with the primary remittance attached, ensuring the coordination-of-benefits amounts match the primary's adjudication exactly. Mismatched COB fields are the most common secondary denial.
Do workers' compensation claims follow the same rules?: No. Workers' comp uses state-specific fee schedules, separate forms and authorization processes, and often paper submission. Timely filing and appeal rights are set by state statute rather than by contract.
What should I do when a payer underpays a contracted rate?: Compare the paid amount to the contracted fee schedule, document the variance, and file a formal underpayment appeal citing the contract. Systematic underpayments are worth auditing in bulk rather than claim by claim.

More on payers

Medicare, Medicaid, commercial and workers' comp rules, tracked payer by payer.

Open the payer directory