Moonlighting as a 1099 NP: Whose NPI Goes on the Claim

Do you bill under your NPI or the practice's?

Both, in different boxes. On a CMS-1500, Item 24J takes the rendering provider's NPI in the lower unshaded portion, and Item 33a takes the NPI of the billing provider or group, a required field 1Ref 1Centers for Medicare & Medicaid Services (2024).Medicare Claims Processing Manual, Chapter 26 — Completing and Processing Form CMS-1500 Data Set.Item 24J takes the rendering provider's NPI in the lower unshaded portion, including the incident-to case in which the supervising practitioner's NPI goes there, and Item 33a takes the NPI of the billing provider or group as a required field.. Your individual NPI says who saw the patient. The practice's NPI says who submits the claim and receives the payment. A 1099 contract does not collapse the two into one.

You do not get a second NPI for the second job. Type 1 covers individual health care providers, including nurse practitioners and sole proprietors, and individuals are only eligible for one NPI 2Ref 2Centers for Medicare & Medicaid Services (2024).The National Provider Identifier (NPI) Fact Sheet.Type 1 covers individual providers including nurse practitioners and sole proprietors, individuals are eligible for only one NPI, and holding an NPI does not establish licensure or credentialing, guarantee payment, or enrol a provider in a health plan.. The same CMS fact sheet is blunt about what the number does not do: it does not establish that you are licensed or credentialed, does not guarantee payment by a health plan, and does not enrol you in one. The difference between npi-1 and npi-2 has its own page. Here, yours is the first kind and the practice's is the second.

But the practice cannot fill in those two boxes and start collecting on its own. Medicare pays a nurse practitioner's professional services only when the nurse practitioner personally performed them, and only when no facility or other provider charges or is paid any amount for furnishing those professional services 3Ref 3Office of the Federal Register / Centers for Medicare & Medicaid Services (2026).§ 410.75 Nurse practitioners' services..Medicare pays an NP's professional services only when the NP personally performed them and no facility or other provider is charged or paid for furnishing them, and supervising other nonphysician staff is not personal performance.. Supervising other nonphysician staff does not count as personal performance.

Item 24J carries one exception on its face. For a service furnished incident to a physician's or non-physician practitioner's service, where the practitioner who ordered it is not the one supervising, the supervisor's NPI goes in the field 1Ref 1Centers for Medicare & Medicaid Services (2024).Medicare Claims Processing Manual, Chapter 26 — Completing and Processing Form CMS-1500 Data Set.Item 24J takes the rendering provider's NPI in the lower unshaded portion, including the incident-to case in which the supervising practitioner's NPI goes there, and Item 33a takes the NPI of the billing provider or group as a required field.. Whether a moonlighting shift can meet incident-to conditions at all is the question behind incident-to or your own npi. If the group instead asks you to render under a physician's number, that is billing under a collaborator's npi, a different arrangement with its own rules.

What the practice needs on file before it can bill your work

A signed reassignment of your Medicare benefits, in place before the first claim goes out. Medicare's default is that it pays nobody but the supplier who furnished the service. A 1099 arrangement runs on the contractual-arrangement exception, under which Medicare may pay an entity enrolled in the Medicare program if there is a contract between the entity and the supplier under which the entity bills for the supplier's services 4Ref 4Office of the Federal Register / Centers for Medicare & Medicaid Services (2026).§ 424.80 Prohibition of reassignment of claims by suppliers..The prohibition on reassignment and the contractual-arrangement exception a 1099 arrangement runs through, plus the conditions: joint and several responsibility for a Medicare overpayment to the entity, and the furnishing supplier's unrestricted access to the claims submitted for that supplier's services..

The employer exception in the same regulation is the W-2 route. Contractors go through the contract exception, and both are exceptions to a prohibition, which is why the paperwork is not optional.

Reassignment of benefits is the CMS-855I's own phrase for it. Reassigning your Medicare benefits allows an eligible organization or group to submit claims and receive payment for Part B services you provided as a member of that group, and the form says such an organization or group may be an individual, a clinic or group practice, or another health care organization 5Ref 5Centers for Medicare & Medicaid Services (2026).Form CMS-855I — Medicare Enrollment Application: Physicians and Non-Physician Practitioners.What reassigning benefits does on the application, that the eligible organization or group may be an individual, clinic, group practice or other health care organization, that both sides must be currently enrolled or concurrently enrolling, that the CMS-855R is discontinued and Section 4F is copied for multiple reassignments, and that revalidation lists every active reassignment..

Two mechanics from the form are worth knowing before you sign. Both sides have to be enrolled: the individual practitioner and the eligible organization or group must be currently enrolled, or concurrently enrolling, the group on the CMS-855B and you on the CMS-855I 5Ref 5Centers for Medicare & Medicaid Services (2026).Form CMS-855I — Medicare Enrollment Application: Physicians and Non-Physician Practitioners.What reassigning benefits does on the application, that the eligible organization or group may be an individual, clinic, group practice or other health care organization, that both sides must be currently enrolled or concurrently enrolling, that the CMS-855R is discontinued and Section 4F is copied for multiple reassignments, and that revalidation lists every active reassignment.. And the old standalone reassignment form is gone. The CMS-855R has been discontinued and every reassignment action is now reported on the CMS-855I. A practitioner reassigning to more than one group copies Section 4F as necessary, and a revalidation application has to list every active reassignment 5Ref 5Centers for Medicare & Medicaid Services (2026).Form CMS-855I — Medicare Enrollment Application: Physicians and Non-Physician Practitioners.What reassigning benefits does on the application, that the eligible organization or group may be an individual, clinic, group practice or other health care organization, that both sides must be currently enrolled or concurrently enrolling, that the CMS-855R is discontinued and Section 4F is copied for multiple reassignments, and that revalidation lists every active reassignment..

What signing the reassignment costs you

Shared liability for money the practice collects on your work. An entity that receives payment under a contractual arrangement and the supplier who would otherwise receive that payment are jointly and severally responsible for any Medicare overpayment to the entity 4Ref 4Office of the Federal Register / Centers for Medicare & Medicaid Services (2026).§ 424.80 Prohibition of reassignment of claims by suppliers..The prohibition on reassignment and the contractual-arrangement exception a 1099 arrangement runs through, plus the conditions: joint and several responsibility for a Medicare overpayment to the entity, and the furnishing supplier's unrestricted access to the claims submitted for that supplier's services.. A recoupment against the group on claims carrying your NPI is not automatically somebody else's problem, and from outside the billing system you would not see it coming.

But the same paragraph gives you an offsetting right: the supplier who furnished the service has unrestricted access to the claims the entity submitted for that supplier's services 4Ref 4Office of the Federal Register / Centers for Medicare & Medicaid Services (2026).§ 424.80 Prohibition of reassignment of claims by suppliers..The prohibition on reassignment and the contractual-arrangement exception a 1099 arrangement runs through, plus the conditions: joint and several responsibility for a Medicare overpayment to the entity, and the furnishing supplier's unrestricted access to the claims submitted for that supplier's services..

Ask for that access in writing before the first shift. Name a person at the practice who will produce claims and remittances on request, set a cadence, and read a month of them early rather than at the end of the contract. The right exists whether or not your contract mentions it, and getting a login or a monthly report is the part that takes a conversation.

The 1099 label answers a tax question

The label does not reach the claim form. Whether the shift is 1099 or W-2 is decided by federal tax law, under the common-law test the IRS applies: behavioral control, financial control, and the type of relationship, with the instruction to look at the entire relationship and at the extent of the right to direct and control the worker 6Ref 6Internal Revenue Service (2026).Independent contractor (self-employed) or employee?.The federal common-law test that decides 1099 versus W-2 status, its three categories of behavioral control, financial control and type of relationship, the instruction to weigh the entire relationship and the right to direct and control the worker, and that misclassification exposure runs to the hiring party.. The claim mechanics above hold either way.

What the classification does change sits on your side of the ledger: withholding, self-employment tax, what the practice reports at year end, and what you set aside quarterly. Getting the classification wrong is primarily the hiring practice's exposure. None of it moves which NPI renders the service or whether a reassignment is on file.

So the tax election and the quarterly math belong with your CPA, who can price the difference against what your own practice already earns. The enrollment record belongs with your Medicare Administrative Contractor.

Reassigning does not raise the rate

The rate follows your NPI wherever the payment is routed. Allowed amounts for the services of a nurse practitioner or clinical nurse specialist may not exceed 85 percent of the physician fee schedule amount, for services other than assistant-at-surgery services furnished on or after January 1, 1998 7Ref 7Office of the Federal Register (2026).42 CFR 414.56 — Payment for nurse practitioners' and clinical nurse specialists' services.The 85 percent of the physician fee schedule ceiling on allowed amounts for NP and clinical nurse specialist services furnished on or after January 1, 1998, other than assistant-at-surgery services, which caps the collections a percentage-of-collections offer is levied on for Medicare work.. Routing the payment through a physician-owned group does not convert your work into physician work, because the ceiling follows the practitioner whose NPI the service is billed under.

That arithmetic matters most when the group offers a percentage of collections. On Medicare patients the collections that percentage is levied on are already capped, so a percentage offer and an hourly offer are not comparable until you know the payer mix behind the shifts. The rest of the arithmetic, and how the ceiling lands across a real schedule, is worked through in the medicare 85% rule for nps.

Before the first moonlighting shift

Four things belong on file before you see a patient at the second site: the group's active Medicare enrollment and the NPI it will put in Item 33a, your reassignment on the CMS-855I, a written route to the claims the regulation already entitles you to see, and a clear answer about which of the group's payer contracts list you at all. The last one has no federal answer, which is why it is the one people skip.

• Confirm the group's enrollment before you accept the NPI it hands you. An NPI does not enrol anyone in a health plan and does not establish that a provider is licensed or credentialed 2Ref 2Centers for Medicare & Medicaid Services (2024).The National Provider Identifier (NPI) Fact Sheet.Type 1 covers individual providers including nurse practitioners and sole proprietors, individuals are eligible for only one NPI, and holding an NPI does not establish licensure or credentialing, guarantee payment, or enrol a provider in a health plan..
• Submit the reassignment on the CMS-855I, Section 4F, and copy that section if you are reassigning to more than one group. Keep your own list, because a revalidation application has to name every active reassignment 5Ref 5Centers for Medicare & Medicaid Services (2026).Form CMS-855I — Medicare Enrollment Application: Physicians and Non-Physician Practitioners.What reassigning benefits does on the application, that the eligible organization or group may be an individual, clinic, group practice or other health care organization, that both sides must be currently enrolled or concurrently enrolling, that the CMS-855R is discontinued and Section 4F is copied for multiple reassignments, and that revalidation lists every active reassignment..
• Put the claims-access right into the contract in plain words, with a named person and a cadence.
• Ask the group's biller which of its commercial contracts list you as a rendering provider, and whether modifier sa belongs on the line for any of them. As a rule commercial credentialing runs contract by contract, and no federal rule settles it for you.

If none of that is in place yet, the order is the group's enrollment, then your reassignment, then the first shift. Work the shift first and the practice is holding claims it cannot legitimately submit under its own number, and you are holding hours nobody can bill.