In most cases you cannot bill before credentialing is complete. Each payer pays only for services on or after the effective date it assigns the provider. Medicare is the main exception, allowing physicians and non-physician practitioners to bill up to 30 days before that date when circumstances prevented earlier enrollment. Medicaid varies by state, and commercial plans generally pay from the contract effective date unless they agree otherwise in writing.
What is a credentialing effective date?
It's the first date of service a payer will pay for a specific provider under a specific enrollment or contract, and it can differ from the day the payer approved them. CMS's Program Integrity Manual draws the line: the date of enrollment is the day the contractor approves the application and can't be made retroactive, while the effective date of billing privileges follows its own rule and can fall earlier.
Commercial plans add a contract step. UnitedHealthcare's credentialing plan says an approved applicant isn't a participating provider on the committee's decision date and can't treat members or be paid until both sides sign the participation agreement with a specified effective date and the provider is loaded into the plan's systems. Log the contract's effective date and confirm the load before you release claims.
How does Medicare set the effective date for a new provider?
For physicians and non-physician practitioners, 42 CFR 424.520(d) sets the effective date as the later of the date the MAC received an enrollment application it later approved or the date the provider first furnished services at the new practice location. The manual confirms the filing date is the date the contractor received the application, on paper or through PECOS.
Timing cuts both ways. A MAC may return an application received more than 60 days before the effective date listed on it, with no appeal rights (42 CFR 424.526), and once the provider starts seeing patients, each day you wait more than 30 days past the start date is a day Medicare won't pay for. File within the 60 days before the start date, once the state license is in hand.
A group also needs the provider's reassignment of benefits, which the manual says is now filed in Section 4F of the CMS-855I because the separate CMS-855R was discontinued. Its effective date follows the same rules, and Medicare enrollment via PECOS covers the filing steps.
How far back does Medicare retroactive billing go?
Up to 30 days before the effective date, under 42 CFR 424.521, when circumstances kept the provider from enrolling sooner, or 90 days if a Presidentially declared disaster under the Stafford Act did. CMS tells contractors to read "circumstances precluded enrollment" as meaning the provider met every program requirement, including state licensure, during those 30 days and had no final adverse action blocking enrollment.
The manual's example shows the math. A physician starts seeing patients on March 1, files on May 1 and is approved on June 1, so the effective date is May 1, the retrospective billing date is April 1, and March services go unpaid. If the MAC rejects an application instead, the provider must file a new one (42 CFR 424.525), and the effective date keys off the new filing date.
Can you bill Medicaid retroactively?
That depends on the state, so read its written policy before counting on it. Missouri's Medicaid program says it will not backdate a provider's enrollment before the date it received the application, except in narrow situations such as out-of-state emergency services. In Texas, the provider procedures manual says the state sets each effective date, claims are allowed only for dates of service on or after it, and new providers must file within 95 days of completing enrollment and within 365 days of the date of service.
Managed care adds a sequence. Under 42 CFR 438.602(b), states must screen and enroll every network provider of their Medicaid managed care plans, and a plan may contract with a provider pending that enrollment for up to 120 days, then must terminate them if the state hasn't enrolled them. Start the state enrollment first; the state-by-state Medicaid guide covers how programs differ.
Do commercial payers allow retroactive credentialing?
Only when the contract or a state rule provides for it, or the plan agrees in writing. Otherwise, expect payment to start on the contract's effective date, as in the UnitedHealthcare plan above, and don't bill against a phone representative's promise.
Some states change the default. Maine's insurance rule for carriers offering managed care plans makes the effective date of credentialing the date the carrier receives a complete application. New York's Public Health Law lets a newly licensed professional, or one who recently moved to New York from another state, become provisionally credentialed when joining a group whose members all participate with the plan, if the plan hasn't decided within 60 days of a complete application. If the plan later declines, the group must refund payments above the out-of-network benefit.
Medicare Advantage plans credential and contract on their own under 42 CFR 422.204, so Medicare enrollment doesn't set a provider's start date with an MA plan. Ask each MA plan for its effective date in writing, as you would a commercial plan.
When can you bill before credentialing is complete, by payer type?
It depends on the payer type, as the table shows. Treat it as a starting point and confirm the details with each payer, since contracts and state rules can change any row.
| Payer type | How the effective date is set | Retro billing possible? | What to confirm |
|---|---|---|---|
| Medicare Part B (physicians and non-physician practitioners) | Later of the date the MAC received the approved application or the first service at the new location | Yes, up to 30 days if every requirement was met, or 90 days if a declared disaster prevented enrollment | Effective and retro dates on the approval, plus the reassignment date |
| Medicaid fee-for-service | Set by the state program | Varies; Missouri generally won't backdate before the application date | The state's written policy and the enrollment notice |
| Medicaid managed care plans | The plan contract, after state Medicaid enrollment | Only if the contract and state rules allow it | The state Medicaid ID first, then the plan's date |
| Commercial plans | Contract effective date after approval and a signed agreement, unless a state rule sets it | Only by contract, written plan agreement or state rule | The written effective date and any retro terms |
Can you bill a new provider's services under another provider's NPI?
Generally, no. Billing under another provider's NPI misstates who delivered the care: Medicare requires the rendering provider's NPI on each service line (Claims Processing Manual, chapter 26), and group claims must identify the physician who performed each service (chapter 1). Medicare allows another NPI only in a few narrow arrangements, none designed for onboarding.
Incident-to services
Under 42 CFR 410.26 and CMS's incident-to guidance, a physician or other practitioner can bill for auxiliary personnel only when they personally performed an initial service and stay actively involved, the service is in a non-institutional setting such as the office, and supervision rules are met. The CY 2026 physician fee schedule final rule made virtual direct supervision by real-time audio and video permanent for incident-to services, except those with a 010 or 090 global surgery indicator. Behavioral health services by auxiliary personnel need only general supervision.
Because the Benefit Policy Manual requires a physician service that starts the course of treatment, a new patient's first visit with the new clinician doesn't qualify. The claim goes under the supervising practitioner's NPI at 100% of the fee schedule, while nurse practitioners and physician assistants billing under their own NPI generally receive 85%. Commercial and Medicaid plans write their own rules, so get each plan's policy in writing.
Substitute physicians: reciprocal billing and fee-for-time arrangements
When a regular physician is unavailable, chapter 1 of the Claims Processing Manual lets the practice bill that physician's NPI for a substitute's visits, with modifier Q5 for a reciprocal arrangement or Q6 for a substitute paid per diem or on a similar fee-for-time basis (formerly called locum tenens). The patient must be seeking the regular physician, the substitute can't cover more than 60 continuous days except for physicians called to active duty, and the practice keeps a record of each service with the substitute's NPI.
In a group, the substitute can't have reassigned benefits to the group, though a group may bill a fee-for-time substitute under a departed physician's NPI for up to 60 days while it hires a replacement. None of this fits a salaried new hire awaiting enrollment, and CMS tells contractors to warn that false Q5 or Q6 certifications can bring civil or criminal penalties or revocation. The locum tenens credentialing guide covers the substitute's paperwork.
What compliance risks come with billing before credentialing is complete?
The main risk is that a claim paid under the wrong NPI or before an effective date becomes an overpayment you have to return. Medicare generally requires identified overpayments to be reported and returned within 60 days under 42 CFR 401.305, and keeping one past that deadline creates an obligation under the False Claims Act. This article is general information, not legal advice, and your payer contracts and state law control, so check the contract and talk with your compliance officer or health care counsel before relying on incident-to, a substitute arrangement or a retroactive date.
What should you do while credentialing is pending?
Start early and schedule the new provider around dates you can confirm. The routine below keeps claims from going out before a payer is ready for them.
- Start early, and time Medicare separately. Begin CAQH updates and commercial applications 90 to 120 days before the start date, and file with Medicare within the 60 days before it.
- Schedule by payer. Book the new provider first with patients whose plans already show them as effective.
- Track effective dates by payer and location. Use the date on the approval letter or contract, never one mentioned on a call.
- Hold claims, but watch filing limits. Medicare allows one calendar year from the date of service under 42 CFR 424.44, and commercial limits sit in each contract.
- Confirm retro terms in writing. Keep the letter or email with the sender's name and a reference number.
If a file is already late, why credentialing applications stall walks through the usual causes, and time-to-revenue for new hires covers the scheduling side. If you'd rather not chase every payer yourself, CredTek's credentialing specialists follow up with providers, payers and boards on a fixed schedule, and clients see each provider's status in a portal.
Frequently asked questions
Does the Medicare approval date become the effective date?
No. The approval date is the date of enrollment, which CMS says can't be made retroactive. The effective date of billing privileges is the later of the date the MAC received the approved application or the date the provider started at the new location, and billing can reach back up to 30 more days if every requirement was met.
Can a nurse practitioner's visits be billed under the supervising physician while enrollment is pending?
Only when every Medicare incident-to condition is met: the physician performed the initial service and stays actively involved, the visit is in a non-institutional setting such as the office, and supervision rules are followed. New patients and new courses of treatment don't qualify. Commercial and Medicaid plans set their own rules, so confirm each policy in writing.
How long can claims be held while waiting for an effective date?
Only as long as each payer's filing limit allows. Medicare requires claims within one calendar year after the date of service, and Texas Medicaid gives new providers 95 days from completing enrollment, capped at 365 days from the date of service. Commercial limits are in each contract, so check the timely filing clause before you hold anything.
What does retroactive credentialing mean with a commercial plan?
It means the plan agrees to pay for services dated before the contract's normal effective date. Unless the contract or a state rule requires it, the plan decides whether to offer it. Maine, for example, sets the effective date of credentialing at the date the carrier receives a complete application. Get any retroactive date in writing first.
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