Billing is one of the least-taught topics in NP school and one of the most consequential once you’re practicing. Getting your credentials wrong, using incident-to billing inappropriately, or starting practice without Medicare enrollment can delay your income, create compliance exposure for your employer, and — in worst-case scenarios — generate False Claims Act liability. The fundamentals aren’t complicated, but they require attention early.
Fast answer: Your first priorities are Type 1 NPI (apply before graduation if possible), Medicare enrollment (PECOS, 60–90 day timeline), and understanding exactly which billing model your employer uses — because incident-to billing has meaningful legal constraints that many employers underexplain.
NPI numbers: Type 1 vs. Type 2, and how to get yours
Every NP needs a Type 1 NPI — a National Provider Identifier that belongs to you as an individual, follows you across jobs, and never changes. This is your permanent professional identifier in the US healthcare billing system. Apply at nppes.cms.hhs.gov. The application is free and takes about 20 minutes. Approval typically comes within 1–10 business days.
Apply before you graduate if your program allows it. Some states permit NPI applications once you have a graduation date; others require your license to be active first. Either way, do not wait until week one of your new job — many onboarding credentialing timelines assume you already have it.
Type 2 NPIs belong to organizations (practices, hospitals, group practices). Your employer will have one. You don’t need to apply for or manage a Type 2 NPI unless you’re opening your own practice.
Common mistake: confusing your NPI with your state license number, DEA number, or taxonomy code. They are separate identifiers. Your taxonomy code (which describes your specialty — e.g., 363L00000X for Family Nurse Practitioners) gets attached to your NPI in the NPPES registry. Make sure it’s correct — it affects how payers classify your claims.
Medicare credentialing: what the process looks like
Medicare enrollment happens through PECOS (Provider Enrollment, Chain, and Ownership System). This is separate from your NPI application. The process involves:
- Creating a PECOS account and submitting an enrollment application (Form CMS-855I for individual practitioners)
- Attaching supporting documents: state license, DEA registration if applicable, education credentials, malpractice insurance
- Waiting for processing — currently 60–90 days for initial enrollments, sometimes longer
You can see patients and bill during the enrollment period using a retroactive billing provision, but only if your employer has submitted your enrollment application before your start date. If enrollment is submitted after you start, claims for that prior period may not be reimbursable. Push your employer to submit on your start date or earlier.
Medicaid credentialing is handled state-by-state through each state’s Medicaid agency — timelines vary from 30 days to 6+ months. If your practice sees significant Medicaid volume, flag this early and ask which state office manages provider enrollment.
Private insurance credentialing (BCBS, Aetna, United, Cigna) happens through each payer individually. Most use the Council for Affordable Quality Healthcare (CAQH) database for applications. Timelines range from 60–120 days per payer. If you’re employed, your employer’s billing staff typically manages this — confirm that your credentialing is in progress within your first week.
Incident-to billing: what it is, when it’s legal, and why it matters
Incident-to billing is a Medicare billing mechanism that allows an NP’s services to be billed under a supervising physician’s NPI at 100% of the physician fee schedule (rather than the standard 85% for NP direct billing). The difference sounds attractive — but incident-to has strict legal requirements that are frequently misunderstood or misapplied.
Legal requirements for incident-to billing:
- The physician must have seen the patient first and established the plan of care
- The NP must be treating an already-diagnosed condition with an already-established plan — not initiating a new diagnosis or new treatment
- The supervising physician must be in the suite (same office suite, not the same building) when the service is rendered
- The service must be “an integral part” of the physician’s professional services
The implication: incident-to billing is only legally available for established patients with established conditions, when the supervising physician is physically present in the office. New patients, new problems, and any visit where the physician is not in the suite must be billed directly under the NP’s NPI at 85%.
Many practices encourage or require incident-to billing without adequately explaining these constraints. This creates real compliance exposure — improper incident-to billing is a False Claims Act issue. If your employer’s billing instructions seem to assume incident-to billing applies broadly across all established patients regardless of physician presence, that’s a conversation worth having with the billing department or a healthcare compliance attorney.
The 85% Medicare reimbursement rate in practice
When billing directly under your NPI, Medicare reimburses NPs at 85% of the physician fee schedule. Here’s what that means in concrete terms:
| Billing model | Who bills | Medicare rate | Legal requirements | Compliance risk |
|---|---|---|---|---|
| Direct NP billing | NP's NPI | 85% of physician fee schedule | NP must be credentialed with Medicare | Low (straightforward) |
| Incident-to billing | Physician's NPI | 100% of physician fee schedule | Physician seen patient first, established plan; physician in suite; established problem only | High if requirements not met |
| Shared/split billing | Either NPI (based on who provided substantive portion) | Varies by who bills | CMS rules on substantive portion (2022 updates) | Moderate — rules changed in 2022 |
The 85% rate is why some physician-owned practices argue that hiring NPs is “less profitable” — the 15% differential does exist. But the math changes significantly when you account for NP salary differentials, patient volume, and practice overhead. From a pure revenue standpoint, a productive NP billing directly at 85% typically generates more revenue than their cost.
For NPs in independent or full-practice authority states, none of this involves a supervising physician at all — you bill directly under your NPI and the incident-to question doesn’t arise. For guidance on what full-practice authority means by state, NP independent practice states covers the current landscape.
Common billing errors that create compliance risk
Beyond incident-to misuse, new NPs should be aware of these recurring issues:
Upcoding: Billing a higher-complexity E/M level (99215) for a visit that doesn’t meet the documentation requirements for that level. Auditors look at the medical decision-making (MDM) documentation — the history, exam, and MDM must support the code billed.
Underdocumentation for the code billed: The inverse of upcoding — billing a lower level because the documentation doesn’t exist to support what was actually done. This leaves revenue on the table and creates inconsistent records.
Split/shared billing errors: CMS updated shared/split billing rules in 2022. The “substantive portion” of a visit (not just presence or attestation) now determines who bills. Review current guidance before assuming old patterns still apply.
Missing co-signature requirements: Some payers and state regulations still require physician co-signature on NP notes for certain visit types. Check your state’s Medicaid requirements specifically — they differ from Medicare.
Billing for services outside your scope: Billing for a procedure or service you’re not credentialed or licensed to perform creates both compliance exposure and potential licensing risk.
What to ask before accepting a job offer
Before you sign an NP employment contract, get clarity on billing arrangements. Useful questions:
- Will I be enrolled in Medicare and Medicaid as an individual provider, or will all services be billed under a physician?
- Does your practice use incident-to billing? If so, can you walk me through the specific criteria you follow?
- Who manages credentialing for private payers, and what’s the typical timeline before I’m credentialed and generating full revenue?
- What happens to patient volume during my credentialing period?
If your potential employer can’t clearly answer these questions, that’s diagnostic. Billing and credentialing confusion at the practice level typically means you’ll encounter it operationally once you start.
For more on evaluating NP employment offers broadly, NP first contract negotiation covers compensation structure, productivity bonuses, and the contract terms that matter most. If you’re deciding between employed and independent contractor arrangements, NP employed vs. independent contractor is a useful parallel read.
Next steps
Once you have your offer in hand:
- Apply for your Type 1 NPI immediately if you haven’t already
- Confirm your employer will submit your Medicare enrollment application on day one of employment
- Ask for a copy of the practice’s billing compliance policies — specifically around incident-to billing
- Request a meeting with the billing department or manager in your first two weeks to understand how your claims will flow
- Keep a personal log of your credentialing status with each payer — don’t rely entirely on employer tracking
Billing literacy early in your career protects you, your employer, and your patients. The NPs who understand this framework from the start spend far less time cleaning up problems later.