Medicaid Billing Guide: Filing Limits, MCO Rules & Balance Billing

Quick Facts (Typical — Your State Rules)

Item	Typical rule
Programme structure	State-administered within federal requirements — 50+ distinct programmes
Timely filing	90–365 days from date of service, state-set
Managed care filing	Set by each MCO contract, often shorter than the state FFS window
Payer order	Payer of last resort — bill all other coverage first
Balance billing the patient	Generally prohibited for covered services
Retroactive eligibility	Common, and usually a recognised filing-limit exception

The Thing That Makes Medicaid Different

Every other payer in your library is one organisation with one provider manual. Medicaid is not a payer — it is a federal framework that each state implements differently. Filing limits, covered services, prior authorisation requirements, fee schedules and appeal processes are all set at state level within federal minimums. A rule you learned billing Medicaid in one state may be simply wrong in the next.

Then a second layer sits on top. Most Medicaid beneficiaries in the United States are now enrolled in managed care, meaning their benefits are administered by a private organisation the state contracts with rather than by the state agency directly. Those MCOs set their own networks, authorisation rules, filing windows and appeal processes. So "what is the Medicaid filing limit" has two answers before you even name the state: the fee-for-service answer and the MCO answer.

Fee-for-Service vs Managed Care

	Fee-for-service	Managed care (MCO)
Claim goes to	State Medicaid agency	The contracted MCO
Rules set by	State manual	The MCO's provider agreement
Filing window	The state's published limit	MCO-specific, often shorter
Prior authorisation	State criteria	MCO criteria, frequently stricter
Appeals	State fair hearing process	MCO appeal first, then state fair hearing

The operational consequence: identify which of the two you are dealing with before you do anything else. The member card names the MCO where one applies. Filing an MCO claim to the state agency, or appealing an MCO denial to the state before exhausting the MCO's own process, both waste the window.

Payer of Last Resort

Federal rules require Medicaid to pay after every other liable source. If the beneficiary has commercial coverage, Medicare, or any third-party liability, that payer must be billed first and its remittance attached when the claim reaches Medicaid.

This produces a specific and avoidable failure. Billing Medicaid first when other coverage exists gets you a denial; by the time you have billed the primary, waited for adjudication and reworked the claim, months have passed and a 90-day state window may be gone. Verify all coverage at registration, not at billing. Where a claim did die this way, good-faith filing with the wrong payer is one of the exceptions most programmes will consider — attach the original payer's denial showing the dates.

You Generally Cannot Bill the Patient

Accepting Medicaid means accepting the Medicaid rate as payment in full for covered services. Participation agreements almost universally prohibit balance billing an enrolled beneficiary — including when Medicaid pays substantially less than your charge, and including when another payer would have paid more. This is a compliance obligation, not a collections choice, and it is one of the more commonly enforced provisions in Medicaid programme integrity.

The narrow exceptions are non-covered services where the patient was properly informed in advance that the service is not covered and agreed to pay, and nominal cost-sharing where the state programme permits it. Both require documentation created before the service, not an invoice created after the denial. This is the same logic as the ABN requirement on the Medicare side — see PR-96 for how advance notice governs whether a non-covered charge is billable to the patient at all.

Retroactive Eligibility

Medicaid eligibility is frequently granted retroactively, covering services that were delivered before anyone knew the patient was covered. Newborns and patients enrolled during an inpatient stay are the classic cases. The result is a batch of claims that could not possibly have been filed on time, because at the time of service there was no coverage to bill.

Most state programmes recognise this as a timely filing exception. The submission needs the eligibility determination attached, showing both the effective date of coverage and the date the determination was issued — the second date is what establishes that you could not have filed sooner. Our timely filing calculator will show how far past the standard window the claim is, which is the figure the exception request needs to address.

How to Find Your State's Actual Rules

Start with the state Medicaid provider manual. Every state publishes one, and the claims submission chapter carries the fee-for-service filing limit and the exception list.

Then get each MCO's provider agreement separately. If you participate with four MCOs in your state, you have five sets of rules including the state's, not one.

Record the window per plan in your practice management system. A single "Medicaid" payer entry covering a state programme and several MCOs with different limits is how claims get filed against the wrong deadline.

Verify eligibility on every date of service. Medicaid eligibility is redetermined periodically and can lapse between visits, which is a materially higher risk than with commercial coverage.

Where Medicaid Sits Against Other Payers

For the windows at every other major payer side by side, see our timely filing limits by payer table. The payer-specific guides for Medicare, Cigna, Humana, Aetna, UnitedHealthcare and BCBS each carry their own filing and appeal detail.

Frequently Asked Questions

What is the Medicaid timely filing limit?

There is no single Medicaid filing limit because Medicaid is administered state by state. Windows commonly fall between 90 and 365 days from the date of service, and managed care organisations within a state frequently set shorter windows than the state's fee-for-service programme. Your state Medicaid provider manual and each MCO contract are the governing documents.

Can I bill a Medicaid patient the balance?

Generally no. Medicaid participation agreements almost universally prohibit balance billing an enrolled beneficiary for covered services, even when Medicaid pays less than your charge or less than another payer would. Accepting Medicaid means accepting the Medicaid rate as payment in full for covered services. Billing the patient the difference is a compliance problem, not a collections strategy.

What is retroactive Medicaid eligibility and how does it affect filing deadlines?

Medicaid eligibility can be granted retroactively, covering services delivered before the determination was made. That creates claims you could not have filed on time because coverage did not exist yet. Most state programmes recognise retroactive eligibility as a timely filing exception - attach the eligibility determination showing the effective date and the date the determination was issued.

What is the difference between Medicaid fee-for-service and Medicaid managed care?

Fee-for-service claims go to the state Medicaid agency and follow the state's fee schedule and rules. Managed care claims go to a private managed care organisation contracted by the state, which sets its own network, prior authorisation requirements, filing windows and appeal processes. Most Medicaid beneficiaries in the United States are now enrolled in managed care, so the MCO's rules usually govern rather than the state's.

Why is Medicaid called the payer of last resort?

Federal rules require Medicaid to pay after all other liable coverage. If a beneficiary has other insurance, that payer must be billed first and its remittance attached when the claim reaches Medicaid. Billing Medicaid first when other coverage exists produces a denial, and the delay while you rework it can push the claim toward the filing limit.

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Medicaid Billing Guide: Every State Is a Different Payer