Evaluation and management (E/M) coding is the system medical practices use to bill for patient visits where a provider assesses a health concern, makes clinical decisions, or manages ongoing care. These codes, ranging from 99202 to 99499 in the CPT code system, represent the most commonly billed category in healthcare. They cover everything from a routine office checkup to a complex hospital admission, but they specifically exclude procedures like surgeries, imaging, and diagnostic tests.
If you’re learning medical coding, transitioning into a billing role, or trying to understand how your practice gets paid, E/M coding is the foundation you need to grasp first.
What E/M Codes Actually Represent
E/M codes capture the intellectual work a provider does during a patient encounter. When a physician listens to your symptoms, reviews your medical history, examines you, considers possible diagnoses, and decides on a treatment plan, that cognitive effort is what E/M coding quantifies. It’s distinct from procedural work. If a doctor evaluates your knee pain (E/M service) and then performs an injection in the same visit (procedure), those are billed separately because they represent different types of work.
The codes are organized into categories based on the setting where care happens and the type of encounter. The major groupings include:
- Office or outpatient visits (99202–99215): the most frequently billed E/M codes, covering visits to a doctor’s office or clinic
- Hospital inpatient and observation care (99221–99239): covering admissions, daily follow-up visits, and discharge services
- Emergency department visits (99281–99285): covering ER encounters at any severity level
- Consultations, nursing facility visits, and other settings: each with their own code ranges within the 99202–99499 spectrum
New Patients vs. Established Patients
For office visits, the first distinction a coder makes is whether the patient is new or established. A new patient is someone who hasn’t received any face-to-face professional service from that physician, or from another physician of the same specialty within the same group practice, in the previous three years. If a patient saw a cardiologist in a group three years and one day ago, they’re considered new again.
This matters because new patient visits (99202–99205) reimburse at higher rates than established patient visits (99212–99215). New patients typically require more work since the provider has no prior relationship or records to build on. Using a new patient code for someone who’s actually established is a common audit trigger.
How Providers Choose a Code Level
Within each category, E/M codes come in levels that reflect how complex the visit was. An office visit for a simple rash and an office visit for a patient with multiple chronic diseases failing treatment are very different in scope, and the coding system accounts for that. Providers select a level using one of two methods: medical decision making or total time spent.
Medical Decision Making
Medical decision making (MDM) is the most common method for selecting a code level. It evaluates three elements: the number and complexity of problems the provider addressed, the amount and complexity of data they reviewed and analyzed (lab results, imaging, outside records, consultations), and the risk of complications or serious harm associated with the management options chosen. Each element falls on a scale from straightforward to high complexity. The two highest of the three elements determine the overall level.
For example, a patient coming in for a medication refill with a well-controlled condition involves straightforward decision making. A patient with three interacting chronic conditions whose test results need careful interpretation, where the treatment options carry significant risk, involves high-complexity decision making and justifies a higher-level code.
Time-Based Selection
Alternatively, providers can select a code level based on the total time spent on the encounter’s date. This includes face-to-face time with the patient plus related work like reviewing records, ordering tests, coordinating care, and documenting. As of 2024, the time thresholds for office visits must be met or exceeded:
- 99202 (new) / 99212 (established): 15 minutes / 10 minutes
- 99203 / 99213: 30 minutes / 20 minutes
- 99204 / 99214: 45 minutes / 30 minutes
- 99205 / 99215: 60 minutes / 40 minutes
One notable exception: emergency department visits cannot be leveled by time. Because ER providers typically manage multiple patients simultaneously over unpredictable timeframes, time doesn’t reliably reflect the complexity of any single encounter. ER visits are leveled by medical decision making only.
Recent Changes to the System
E/M coding underwent significant restructuring in recent years. In 2021, office visit guidelines were overhauled to simplify level selection. In 2023, the AMA extended those same principles to inpatient and observation settings, making the requirements more uniform across care settings. The 2023 changes also merged previously separate observation care codes into the hospital inpatient category and deleted standalone consultation codes for inpatient settings.
The 2024 update refined time-based coding further. Previously, office visit time thresholds were expressed as ranges (for instance, 15–29 minutes for code 99202). Now each code has a single minimum that must be met or exceeded, eliminating ambiguity about where one level ends and the next begins.
These changes reflect a broader trend: moving away from documentation volume as the basis for billing and toward the complexity of the clinical thinking involved.
Medical Necessity: The Core Requirement
Every E/M code billed must be medically necessary. This is the overarching criterion for payment, sitting above all other requirements. In practical terms, it means the level of service billed has to match what the patient’s condition actually required. A provider who bills a high-complexity visit for a straightforward problem, even if the documentation technically supports it, is billing inappropriately.
CMS guidelines explicitly state that the volume of documentation should not be the primary influence on which level of service is billed. Writing a longer note doesn’t justify a higher code. What justifies it is the actual clinical complexity of the problems addressed, the data analyzed, and the risk involved in the management decisions.
Modifiers That Affect E/M Billing
Modifiers are two-digit codes appended to an E/M code to indicate special circumstances. Two of the most commonly used in E/M coding are Modifier 25 and Modifier 57.
Modifier 25 signals that a provider performed a significant, separately identifiable E/M service on the same day as a procedure. For instance, if a patient comes in for a scheduled mole removal but also needs evaluation of new chest pain symptoms, the E/M service for the chest pain can be billed alongside the procedure using Modifier 25. The key requirement is that the E/M service must be genuinely separate from the work already included in the procedure’s code, and the documentation must support that.
Modifier 57 applies when an E/M visit results in the decision to perform surgery. If a patient presents with abdominal pain, and during the evaluation the surgeon determines an operation is needed, Modifier 57 is appended to that E/M visit. This tells the payer the visit wasn’t part of the surgical package; it was the encounter where the surgical decision was made.
Prolonged Services
When a visit exceeds the maximum time threshold for the highest-level code in a category by at least 15 minutes, providers can bill an additional prolonged services code. This captures the extra work involved in unusually long or complex encounters.
One complication worth knowing: CMS and the AMA have different rules for reporting prolonged services. CMS created its own billing codes for Medicare patients, which differ from the CPT codes the AMA publishes. Practices that see both Medicare and commercial patients need to track which set of rules applies to each payer, making this one of the trickier areas of E/M billing to get right.