The Stark Law and Physician Self-Referral in Medical Billing

The Stark Law is found at 42 U.S.C. § 1395nn, a Medicare provision of the Social Security Act titled “Limitation on certain physician referrals.” It states a single conditional rule with two halves. If a physician — or an immediate family member of that physician — has a financial relationship with an entity, then the physician may not make a referral to that entity for the furnishing of a designated health service for which payment may be made under Medicare, and the entity may not present, or cause to be presented, a claim or bill for a designated health service furnished pursuant to a prohibited referral. One half restrains the physician; the other restrains the biller.

That second half is why the law belongs in a billing team's field of vision and not only a lawyer's. The prohibition is not just on referring — it is on billing. An entity that furnishes a designated health service under a referral the statute forbids cannot lawfully submit the claim for it, so a Stark problem does not stay in the back office where the arrangement was signed; it lands on the claim. This is one of the specific rules the Compliance and Regulations category exists to keep straight, because the compliance program is the system that is supposed to catch an at-risk arrangement before it becomes a stream of claims.

The trigger the statute defines most broadly is the financial relationship. It comes in two forms: an ownership or investment interest in the entity, or a compensation arrangement between the physician (or an immediate family member) and the entity. Either one is enough. A physician who owns a share of an imaging center has a financial relationship with it; so does a physician who is paid a medical-director stipend by a lab or who leases office space to a home-health agency. Because the relationship can be a payment flowing in either direction, an arrangement that looks like an ordinary business dealing can still be the financial relationship that makes a referral a violation.

The Stark Law does not restrict every referral. It restricts referrals for a designated health service — a defined set the statute enumerates as twelve categories at § 1395nn(h)(6). In plain terms they are: clinical laboratory services; physical therapy; occupational therapy; outpatient speech-language pathology; radiology and certain other imaging services, including MRI, CT, and ultrasound; radiation therapy services and supplies; durable medical equipment and supplies; parenteral and enteral nutrients, equipment, and supplies; prosthetics, orthotics, and prosthetic devices and supplies; home health services; outpatient prescription drugs; and inpatient and outpatient hospital services.

For most of those categories, whether a specific service counts as a DHS is not left to judgment. CMS publishes an annually updated list of the CPT and HCPCS codes that are designated health services, so the answer for a given service is a lookup against the current year's list rather than an argument. A few categories — inpatient and outpatient hospital services and home health services among them — are defined by their nature instead of by a code list. Because the list is revised each year, the version that governs is the current one.

The single most important thing to understand about the Stark Law is that it is a strict-liability statute. OIG states it plainly: proof of specific intent to violate the law is not required. There is no “we didn't mean to” defense to the referral-and-billing prohibition. If a physician with a financial relationship refers a Medicare patient for a designated health service and no exception applies, the referral is prohibited and the entity may not bill — regardless of whether anyone intended to do anything wrong, and regardless of whether the arrangement was priced fairly or negotiated in good faith.

That is a different kind of law from the ones a billing team usually meets. Most fraud-and-abuse exposure turns on a state of mind — a false statement made knowingly, a payment made to induce referrals. Stark removes the state of mind from the core prohibition. It behaves less like a fraud statute and more like a bright-line rule: cross it and the claim is not payable, whatever was in anyone's head. The practical consequence is that good faith is not protection, and a technically defective arrangement — one that would have fit an exception but for a missing signature or an expired term — can put an entire stream of claims outside the law.

Because the prohibition is written broadly enough to catch arrangements that are ordinary and necessary — physicians do own equipment, employ each other, rent space, and provide services within their own practices — the statute and its regulations carve out exceptions. An arrangement that fits an exception completely is permitted, and the referral and the bill are lawful. The exceptions fall into three families: general exceptions that apply to both ownership and compensation relationships, exceptions that apply only to ownership or investment interests, and exceptions that apply to compensation arrangements.

The names give the flavor of what they protect. Among the general exceptions are physician services and the in-office ancillary services exception — the one that lets a group practice furnish many designated health services to its own patients. On the compensation side sit exceptions for the rental of office space and equipment, bona fide employment relationships, and personal service arrangements. Each exception is a named category followed by a list of conditions, and the conditions are the whole point.

The exceptions are also where the law has moved most recently. CMS's 2020 “Modernizing and Clarifying the Physician Self-Referral Regulations” final rule, effective in January 2021, added exceptions for certain value-based compensation arrangements and clarified terms the exceptions turn on — fair market value, commercial reasonableness, and what it means for compensation to take into account the volume or value of referrals. The details are a matter for counsel, but the direction matters to a billing operation: the definitions that decide whether an arrangement fits an exception are themselves subject to change, so “it qualified last year” is not the same as “it qualifies now.”

The Stark Law is one of three fraud-and-abuse laws named together so often that they blur into one. They are not one. The Anti-Kickback Statute and the False Claims Act ask different questions, require different proof, and expose a practice to different things — and the differences change what a billing operation watches for.

The cleanest way to hold the three apart: Stark asks a yes-or-no question about a physician's financial relationship and a defined list of services and does not care about intent, so it is strict; the Anti-Kickback Statute asks about intent and reaches anyone and any federal-program service, so it is criminal; and the False Claims Act is the collector, turning a violation of either — or an ordinary billing lie — into liability on the claim itself. Stark and the Anti-Kickback Statute also overlap in fact: a single arrangement, such as an above-market medical directorship tied to referrals, can implicate both at once.

A billing team rarely negotiates the arrangements Stark governs, but it is uniquely placed to see their output, because the law's consequence shows up as a claim that should not be billed. The posture is not to become a self-referral lawyer; it is to recognize an at-risk referral and route it before it turns into a pattern of unbillable claims.

1. 01

   Know where the financial relationships are

   Stark risk lives wherever a referring physician has an ownership stake in, or a payment arrangement with, the entity a designated health service is billed under — an in-house lab or imaging suite, a leased space, a medical directorship, a management fee. A practice that has mapped those relationships can tell, for a given DHS claim, whether the referral behind it needs to have fit an exception.
2. 02

   Treat a DHS referral from a related entity as a claims question

   When the service is a designated health service and the referring physician has a financial relationship with the billing entity, the arrangement should have been vetted against an exception before the first claim went out. If no one can point to the exception it fits, that is a signal to stop and check, not to bill and hope.
3. 03

   Escalate, do not adjudicate

   Whether an arrangement fits an exception is a legal judgment, not a claim-desk call. Route it to the compliance program and to qualified health care counsel, who can test it against the specific exception and its conditions. A documented escalation is exactly what a compliance program's reporting and response elements are built to receive.
4. 04

   Handle a discovered problem as a refund, and consider self-disclosure

   If a designated health service was billed under a referral that fits no exception, the amounts collected generally have to be refunded on a timely basis, and retaining them can turn an error into False Claims Act exposure. CMS operates a Self-Referral Disclosure Protocol — created by the Affordable Care Act and separate from OIG's self-disclosure protocol — through which a provider can disclose an actual or potential Stark violation. Whether and how to use it is a decision for counsel and the compliance program, not the billing desk.

Screening is the other place billing and Stark risk meet. Because a Stark violation can end in exclusion, the same exclusion screening a practice runs on its workforce and vendors is part of keeping an excluded party off its claims, and the same compliance program that reviews financial arrangements up front is what answers the self-referral question before an auditor asks it. The controls reinforce each other: map the relationships, vet them against the exceptions, and route what does not clearly fit.