Billing and Coding Clarity: The Top 5 Questions Answered
Get clear answers to your top billing and coding questions
Let’s face it: Medical billing and coding can often feel like a moving target. Between shifting Medicare guidelines, strict modifier requirements, and conflicting commercial payer rules, staying compliant while protecting your practice’s revenue requires constant vigilance.
To help clear up the confusion, we’ve rounded up the five most common — and complex — billing and coding questions our team receives. We featured a webinar on this topic, and below is a breakdown of what we covered, drawing on insights from Ronda Tews, Vice President of Billing and Coding Compliance at ModMed.
Can a PA or NP bill under a physician’s NPI for every patient?
The short answer: no. When a physician assistant (PA) or Nurse practitioner (NP) bills under a supervising physician’s NPI, it is known as incident-to billing. While this can be a great way to leverage your advanced practice providers, Medicare has strict rules for when this is allowed:
- Incident-to billing requirements: Incident-to billing does not apply to new patients or established patients presenting with a new problem. The physician must perform the initial visit and set the plan of care.
- Direct supervision: The supervising physician must be physically present in the office suite and immediately available to assist if needed. Effective 1/1/26, Medicare allows the supervision requirement to be met via audio/visual technology if the services provided as incident-to do not have a 10- or 90-day global period.
- Mandatory enrollment: Even if the NPP only plans to bill incident-to, the nonphysician practitioner (NPP) must be formally enrolled in Medicare.
Check your commercial payer contracts carefully. Many commercial payers are phasing out incident-to billing entirely and require NPPs to bill under their own NPIs for every visit. Also, some payers have their own incident-to guidelines that you must follow. Many commercial payers require identification on the claim that incident-to services were performed by appending modifier SA to the CPT and/or populating the Rendering Provider (box 24j) on the claim.
Can we bill for an uncredentialed physician under an established physician’s NPI?
Generally, no. It may be tempting to try and bypass credentialing delays by billing a new doctor’s services under an established partner’s NPI, but this practice often leads to automatic claim rejections and audits. Medicare strictly prohibits this outside of two specific scenarios.
Exceptions for a physician billing under another physician:
- Substitute physicians (locum tenens): If a regular physician is unavailable due to illness, vacation, or sabbatical, a substitute physician can fill in for up to 60 days. This requires either a reciprocal billing arrangement (using the Q5 modifier) or a fee-for-time compensation arrangement (using the Q6 modifier). Note: Medicare does not allow locum tenens billing for NPPs.
- Teaching physicians: Residents can bill under a teaching physician using the GC or GE modifiers, depending on primary care exceptions.
What is the billing difference between an office-based procedure room and an ASC?
The difference comes down to place of service (POS) codes, regulatory compliance, and reimbursement rates. While an office-based procedure room might look like a surgery center, it is billed very differently.
Office-based procedures (POS 11)
These are billed as part of the physician’s private practice. Even if it is a dedicated surgical suite, it uses the standard office POS code. State regulations for licensure vary, but it operates under the practice’s umbrella. Accreditation of the office-based procedure room does not change the POS either.
Ambulatory surgery center (POS 24)
An ASC is a highly regulated, distinct legal entity. It requires separate facility and professional billing (UB-04/1500), strictly separate electronic medical records, and specific Medicare certification. Physician professional fees are often reduced in an ASC because the facility itself receives a separate technical fee.
Are there specific requirements for documenting injections?
Yes, and they have been a target for audits. Payers expect extremely precise documentation for single-dose containers. Gone are the days of simple, one-line injection notes. To pass an audit, your documentation must include:
- The medication name
- The exact dosage administered, recorded in both milligrams (mg) and milliliters (mL)
- The method of administration and frequency
Documenting drug wastage
Crucially, you must account for wastage. You must explicitly document any discarded medication, even if it is less than one unit:
- Use the JW modifier (on a separate claim line) to report the exact amount of the drug that was discarded
- Use the JZ modifier to attest that zero drug amount was discarded
If a physician changes practices, can they bill patients who follow them to their new location as new?
No, unless three full years have passed. A common misconception is that because the physician is billing under a new practice’s tax ID, the patients can be reset as new, but this is incorrect.
The AMA guidelines and Medicare Claims Processing Manual dictate that the definition of a new versus established patient is based on the face-to-face relationship between the patient and the physician — not the building they are standing in or the tax ID they are billing under.
If the physician (or another physician of the exact same specialty and subspecialty within the same group) has provided professional services to that patient within the past three years, they are an established patient.
Need help keeping up with billing and coding changes?
Staying compliant means staying proactive, but navigating the nuances of commercial payer policies and Medicare guidelines doesn’t have to fall entirely on your shoulders.
By using revenue cycle management (RCM) software and services like those offered by ModMed®, you can gain a dedicated team that proactively scrubs claims for missing information and manages complex denials on your behalf. Additionally, the ModMed EHR platform auto-suggests CPT and ICD-10 codes based on your clinical documentation. Together, this combination of software and service is designed to help you capture strict requirements — like injection wastage and incident-to details — before claims go out the door.
This blog is intended for informational purposes only and does not constitute legal or medical advice. Please consult with your legal counsel and other qualified advisors to ensure compliance with applicable laws, regulations, and standards.
