Work through the ten groups in order, because diagnosis conventions and E/M foundations come before modifier, payer, and privacy applications. For each concept, read the rule, then the worked example with its resolved decision, and finish with the mistake note to lock in the distinction. Concepts are drawn from the ICD-10-CM official guidelines, E/M study material, and HIPAA privacy text, so keep current code books beside you. Treat this as teaching support alongside official materials, not a syllabus or a substitute for them.
ICD-10-CM Structure and Conventions
1. Alphabetic Index to Tabular List workflow
Diagnosis coding begins with the main term in the Alphabetic Index, following all cross-references and see-also entries, then verifying the code in the Tabular List, where notes, definitions, and instructions govern the final assignment. A code located in the index is never final until the tabular entry is read completely.
Example: A note documents an upper respiratory infection; the coder locates the main term under infection, respiratory tract, upper, then confirms the code in the Tabular List before reporting it.
Mistake to avoid: Assigning a code straight from the Alphabetic Index without verifying tabular instructions and any required additional characters.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
2. Placeholder X and 7th characters
Codes with an applicable 7th character are invalid without it, and when the base code is shorter than six characters a placeholder X fills the empty positions so the 7th character stays in the seventh position. Only full codes, never categories or subcategories, may be reported on a claim.
Example: A five-character injury code requiring an initial-encounter character must be reported with X padding so the encounter character lands in position seven, or the code is invalid.
Mistake to avoid: Dropping the placeholder X and appending the 7th character directly to a shorter code, producing an invalid code.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
3. Excludes1 versus Excludes2 notes
An Excludes1 note means the excluded code is not coded with the code above it because the two conditions cannot coexist, such as congenital versus acquired forms of the same condition; the stated exception is that when the two conditions are unrelated to each other, both codes may be reported. An Excludes2 note means the excluded condition is not part of the code but may be reported together when the patient truly has both. If it is not clear whether two conditions tied by an Excludes1 note are related, query the provider.
Example: A patient with documented sleep-related teeth grinding and a clearly unrelated somatoform condition may have both codes reported despite an Excludes1 note, because the conditions are unrelated.
Mistake to avoid: Treating every Excludes note as an absolute bar and deleting a code the documentation genuinely supports under an Excludes2 note or an unrelated-conditions Excludes1 exception.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
4. Etiology and manifestation sequencing
When one underlying condition produces manifestations in multiple body systems, the etiology code is sequenced first and the manifestation second, guided by code first and use additional code notes. Manifestation titles reading in diseases classified elsewhere may never stand as first-listed or principal diagnoses.
Example: For dementia in Parkinson's disease, the Parkinson's etiology code is sequenced first with the dementia manifestation code following it, never in the reverse order.
Mistake to avoid: Reporting a manifestation code in diseases classified elsewhere as the first-listed diagnosis without its underlying etiology code.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
5. The with convention presumption
The words with or in between two conditions in a title, index entry, or tabular note are interpreted as associated with or due to, and the classification presumes a causal link even without explicit provider documentation, unless the documentation clearly states the conditions are unrelated or another guideline requires documented linkage.
Example: An index entry linking diabetes with a circulatory complication allows both to be coded as related without the provider explicitly connecting them, unless the note states they are unrelated.
Mistake to avoid: Separating conditions the classification already presumes related, or coding them as related when documentation clearly calls them unrelated.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
6. Other specified versus unspecified codes
NEC entries direct the coder to an other specified code when no specific code exists for a documented condition, while unspecified codes are used only when the record lacks detail for anything better. For categories lacking an unspecified code, the other specified code may serve both purposes.
Example: A documented rare condition with no dedicated code is assigned the other specified code in that category rather than a vague unspecified code, because the documentation supports greater specificity.
Mistake to avoid: Defaulting to an unspecified code when the documentation clearly supports an other specified entry.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
Outpatient Diagnosis Selection and Sequencing
7. First-listed diagnosis selection
In outpatient coding the first-listed diagnosis describes the most significant reason for the visit, generally reflecting the chief complaint, while coexisting conditions and relevant histories are reported secondarily. Only codes supported by that encounter's documentation may be assigned, since each date of service must stand alone.
Example: A visit for cough and fever with stable, unaddressed hypertension reports the respiratory reason first; the hypertension is omitted because it was not treated or an active factor.
Mistake to avoid: Sequencing a chronic condition first merely because the physician listed it first in the assessment.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
8. Uncertain diagnoses are not coded
Terms such as probable, suspected, likely, rule out, consistent with, and compatible with do not support a diagnosis code in outpatient reporting. Code the highest level of certainty known, using signs, symptoms, and abnormal test results until a definitive diagnosis is established by the provider.
Example: A provider suspects breast cancer in a patient with a breast mass; the coder reports the breast mass code, not cancer, until pathology confirms the diagnosis.
Mistake to avoid: Reporting a suspected malignancy or other unconfirmed condition as though it were an established diagnosis.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
9. Interpreted test results rule
For outpatient diagnostic tests interpreted by a physician whose final report is available at the time of coding, report confirmed or definitive diagnoses documented in the interpretation, and do not add related signs and symptoms when a definitive diagnosis is known. For normal results, code the sign or symptom that necessitated the study.
Example: A chest X-ray interpreted as pneumonia supports reporting pneumonia alone; a normal film after a complaint of persistent cough is coded to the cough.
Mistake to avoid: Reporting both the confirmed finding and its integral signs and symptoms as separate additional diagnoses.
Reference: AAPC CEMC study guide sample
10. Postoperative diagnosis governs
When documentation provides both preoperative and postoperative diagnoses and they differ, the postoperative diagnosis codes are reported. The preoperative impression is treated as uncertain until the procedure reveals the actual condition, mirroring the rule against coding unconfirmed diagnoses in outpatient reporting.
Example: A lesion excised under a preoperative impression of cyst but found at procedure to be an abscess is coded to the abscess, the postoperative diagnosis.
Mistake to avoid: Reporting the preoperative impression when the postoperative diagnosis differs and is documented.
Reference: AAPC CEMC study guide sample
11. Follow-up Z codes after completed treatment
Categories Z08, Z09, and Z39 are reported when the condition has been fully treated and no longer exists and the main reason for the encounter is a follow-up examination with no further treatment planned. In that situation the follow-up Z code is reported as the first-listed code.
Example: A patient returns for a completed-treatment fracture recheck with no further therapy planned; the encounter is coded to the follow-up Z code first rather than the old fracture.
Mistake to avoid: Coding the original condition as though it still exists after treatment is complete and only surveillance remains.
Reference: AAPC CEMC study guide sample
12. Chronic conditions reported only when active
Report a chronic condition only when it is treated at the encounter or becomes an active factor in the patient's care, and never report conditions that no longer exist or do not pertain to the visit. Many patients carry numerous chronic complaints that stay off the claim unless actually addressed.
Example: A routine visit addressing only diabetes omits the patient's historically documented, unaddressed hypothyroidism because it was not treated or considered during this encounter.
Mistake to avoid: Listing every historical chronic diagnosis on each claim regardless of whether the encounter addressed it.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
Condition-Specific Diagnosis Rules
13. Diabetes type default and medication status codes
When the record does not indicate diabetes type but shows insulin use, assign the type 2 diabetes code and add category Z79 codes for long-term current use of insulin, oral hypoglycemics, or injectable non-insulin drugs. The long-term insulin code is not assigned for insulin given temporarily to control blood sugar during an encounter.
Example: A type 2 patient on both oral medication and long-term insulin receives the diabetes code plus both medication Z79 codes, but not for a one-time in-office insulin dose.
Mistake to avoid: Assigning the long-term insulin code for temporary insulin administered during a single encounter.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
14. Combination codes for concurrent conditions
Some ICD-10-CM codes describe two conditions at once, such as hypertension with chronic kidney disease or acute and chronic cholecystitis in a single code. Read all Includes, Excludes1, and Excludes2 notes before choosing, because two separate codes are unnecessary and often wrong for these documented pairings.
Example: Documented hypertension with chronic kidney disease is reported with one combination code from the appropriate category rather than separate hypertension and kidney disease codes.
Mistake to avoid: Splitting a combination code into two separate codes the classification already joins together.
Reference: AAPC CEMC study guide sample
15. Sequela coding without a time limit
Sequela, or late effect, codes are usually reported as secondary diagnoses with the effect or reason for the visit primary, and there is no time limit within which late effects must appear. For cerebrovascular disease, the late-effects category captures neurologic deficits from earlier stroke and may accompany current-stroke codes when both exist.
Example: A patient with an old stroke and residual weakness presenting for weakness management reports the sequela category code secondary, with no current acute stroke code.
Mistake to avoid: Applying an arbitrary time window after the original event to decide whether a condition counts as a sequela.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
16. Acute on chronic sequencing
When a condition is documented as both acute or subacute and chronic and no single code describes the combination, the acute or subacute code is reported first-listed with the chronic code secondary. The provider's documentation, not coder inference, establishes which phase the condition is in.
Example: A flare of a chronically inflamed joint documented as both acute and chronic is sequenced with the acute code first and the chronic code second when no combined code exists.
Mistake to avoid: Sequencing the chronic code first or assuming acuteness the documentation never states.
Reference: AAPC CEMC study guide sample
17. Dominance defaults for late effects
For sequela codes specifying hemiplegia, hemiparesis, or monoplegia, when dominance is not stated and the classification provides no default, ambidextrous patients default to dominant, left-side involvement defaults to nondominant, and right-side involvement defaults to dominant. These defaults exist precisely to resolve encounters with undocumented handedness, so the code assignment is completed without resorting to an unspecified dominance code.
Example: A right-sided weakness sequela in a patient whose handedness is undocumented is coded using the dominant-side default that applies to right-sided involvement.
Mistake to avoid: Assigning an unspecified dominance code when a documented default rule resolves the selection.
Reference: AAPC CEMC study guide sample
18. Non-provider documentation exceptions
Code assignment is based on the documenting provider's entries, with limited exceptions where other clinicians' documentation may be used, including BMI, pressure ulcer stage, coma scale, laterality, social determinants of health, blood alcohol level, underimmunization status, and firearm injury intent.
Example: A nurse's recorded BMI may support the BMI code even though the provider did not restate it, because BMI is an accepted non-provider documentation exception.
Mistake to avoid: Building diagnosis assignments from nursing notes for conditions outside the listed exception categories.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
E/M Documentation Foundations
19. History and exam no longer level the visit
Under the revised AMA guidelines, a medically appropriate history and/or examination, when performed, is included in the service; it should be documented but is not used to determine the code level for office and other outpatient services. Leveling rests on medical decision making or total time instead.
Example: An exquisitely detailed physical exam with minimal decision making still levels to the MDM-supported code, because exam detail no longer raises the office visit level.
Mistake to avoid: Counting exam elements or history bullets to support a higher office E/M level.
Reference: AAPC CEMC study guide sample
20. Two acceptable leveling methods
The level of an E/M service is selected based on either the level of medical decision making as defined for the service, or the total time for E/M services performed on the date of the encounter. The provider may choose the method case by case, and documentation must support whichever is used.
Example: A visit with moderate MDM but modest documented time is leveled by MDM to the moderate-level established patient code rather than by time.
Mistake to avoid: Mixing elements of both methods to construct a level supported by neither alone.
Reference: AAPC CEMC study guide sample
21. The minimal-service office visit
The lowest office visit code is reported for services that typically do not require the presence of a provider, and the concept of medical decision making does not apply to it. Clinical staff work, not physician analysis, drives this code, distinguishing it from every level that requires MDM or time.
Example: A nurse rechecking a stable established patient at the physician's direction supports the minimal-service code because no provider presence or decision making is required.
Mistake to avoid: Attempting to grade medical decision making for the code where MDM does not apply.
Reference: AAPC CEMC study guide sample
22. New versus established patient status
E/M categories divide by patient status, and the same documentation levels to different codes for new versus established patients. The mapping from straightforward, low, moderate, and high MDM to specific codes differs across the two columns, so patient status must be settled before any level is assigned.
Example: Low MDM maps to a mid-range new-patient code and a lower established-patient code; misreading a returning patient as new inflates the billed level.
Mistake to avoid: Assigning a new-patient code for a patient the practice has previously seen.
Reference: AAPC CEMC study guide sample
23. Baseline documentation principles
Documentation must be legible to someone other than the documenting provider and staff, must readily demonstrate the date of service, the patient's name, and the provider's name, and must support the nature of the visit and the medical necessity of the services rendered before any leveling method is applied.
Example: An unsigned note lacking a date cannot support any E/M claim regardless of its clinical content, because attribution and date are baseline requirements.
Mistake to avoid: Leveling a visit from clinical content while the note lacks date, patient, or provider identification.
Reference: AAPC CEMC study guide sample
24. Medical necessity as the ceiling
Regardless of whether MDM or time determines the level, documentation should support the medical necessity of the visit, and payers may regulate when each method is used. Coders report from documentation; final determinations of what constitutes medical necessity belong to physician peer review, not the coder.
Example: A time-documented visit whose content shows a trivial problem is reported at the level the documentation supports, since time alone does not override necessity limits.
Mistake to avoid: Treating a documented time total as an automatic level regardless of what the encounter's content supports.
Reference: AAPC CEMC study guide sample
Leveling by Medical Decision Making
25. Three components of medical decision making
Medical decision making is graded as straightforward, low, moderate, or high using three components: the number and complexity of problems addressed at the encounter, the amount and complexity of data reviewed and analyzed, and the risk of complications, morbidity, or mortality of patient management, per the CPT definitions and MDM table.
Example: An established visit with an acute uncomplicated illness, limited data, and prescription drug management resolves to low overall MDM because the elements combine per the table.
Mistake to avoid: Leveling from a single favorite component, such as risk alone, without weighing all three.
Reference: AAPC CEMC study guide sample
26. Counting problems addressed
A problem counts toward the number and complexity of problems only if it is addressed within that encounter. One self-limited or minor problem, such as an uncomplicated cold or sore throat, yields straightforward MDM, while two self-limited or minor problems raise the element to low.
Example: A patient with both a sore throat and a mild insect bite reaction has two minor problems, moving the number-of-problems element from straightforward to low.
Mistake to avoid: Counting every listed historical problem rather than only those the encounter actually addresses.
Reference: AAPC CEMC study guide sample
27. Conditions managed by another provider
When documentation merely states a patient has a condition being treated by another provider, that condition is not considered in leveling the visit. It becomes countable only with additional documentation showing assessment or care coordination regarding that diagnosis beyond the statement of outside treatment.
Example: A note listing thyroid disease managed by an endocrinologist, with no assessment or coordination, excludes that disease from the problem count; a documented medication review would include it.
Mistake to avoid: Counting a passively mentioned diagnosis managed by another provider as a problem addressed at this encounter.
Reference: AAPC CEMC study guide sample
28. Comorbidities must be addressed to count
Comorbidities and underlying diseases do not influence the level unless they are addressed and increase the data reviewed or the risk of management; simply listing a chronic illness is insufficient. The final diagnosis alone does not determine complexity, since extensive work may be needed to exclude a highly morbid condition.
Example: A note listing diabetes without addressing it cannot use diabetes to raise risk, but documented management adjusting treatment because of it can support a higher level.
Mistake to avoid: Inflating risk by counting every chronic illness in the history, addressed or not.
Reference: AAPC CEMC study guide sample
29. Data rules for tests and interpretations
A test counts toward the data element only when it is not separately reportable; ordering or interpreting a test whose professional interpretation is separately billed, such as an X-ray or ECG performed in office, does not count. Results-only tests like a rapid strep may be counted, but reviewing results ordered at a prior encounter does not.
Example: A rapid point-of-care strep test performed and analyzed in office counts toward data even though billed, while an in-office ECG with separately billed interpretation does not.
Mistake to avoid: Counting a separately billed interpretation or a follow-up re-review of previously ordered results as new data.
Reference: AAPC CEMC study guide sample
30. Risk of patient management
Risk is assessed by the physician's judgment of the likelihood of illness, complications, or mortality between the current visit and the next scheduled encounter, and is separate from the inherent risk of the condition itself. Management decisions made during the encounter, such as prescription drug management, drive the risk level.
Example: Starting a prescription drug regimen for an acute illness supports moderate risk even when the diagnosis itself carries a favorable outlook, because management decisions set the level.
Mistake to avoid: Grading risk by the diagnosis name rather than by the management decisions documented in the encounter.
Reference: AAPC CEMC study guide sample
Time-Based Leveling and Prolonged Services
31. Total time on the date of the encounter
When time is used, the level is based on the total time for E/M services performed on the date of the encounter. This is a date-of-service total tied to the E/M services rendered that day, and it stands as the alternative to leveling the same visit by medical decision making.
Example: A physician who documents a total time for one patient's E/M services across that date may level the visit by that total rather than by MDM.
Mistake to avoid: Leveling by time from an estimate or from minutes spent on a different date.
Reference: AAPC CEMC study guide sample
32. Documented total time requirement
To use time as the criteria for selecting an E/M level, the provider must document the total time spent in patient care on the date of the encounter. Without a documented total, neither time-based leveling nor a prolonged service code is supportable from the note.
Example: A note stating only that the visit ran several minutes longer than usual cannot be leveled by time; the coder reverts to the MDM-supported level.
Mistake to avoid: Selecting a time-based level or prolonged code from a qualitative remark about extra time.
Reference: AAPC CEMC study guide sample
33. Prolonged services need a time total
Prolonged service add-on codes report extended time beyond the base visit, but they require a documented total time. A narrative remark about spending longer than usual, without a total, supports neither the add-on code nor a higher base level selected by time.
Example: A note describing extended counseling for a patient newly starting anticoagulation, with no total time documented, yields no prolonged service add-on; the visit is leveled by its medical decision making instead.
Mistake to avoid: Appending a prolonged service code whenever the note mentions extended counseling.
Reference: AAPC CEMC study guide sample
34. Prolonged services are reported with a base code, not instead of one
A prolonged service code is reported in addition to the base E/M code for the encounter, never as a stand-alone service and never as a swap for a higher base level. Both prolonged service reporting and time-based leveling depend on a documented total time for the E/M services performed on the date of the encounter; that documented total is what separates a visit that merely ran long in the narrative from one that quantifiably supports extended service reporting.
Example: A physician documents a total time on the date of the encounter well beyond what the visit level otherwise supports; the extended time is captured by reporting the prolonged service code together with the base E/M code, and the coder does not guess a higher level the note does not support.
Mistake to avoid: Reporting a prolonged service code without a base E/M code, or substituting a single higher-level base code for the base-plus-prolonged structure.
Reference: AAPC CEMC study guide sample
35. Increased procedural services modifier excludes E/M
The increased procedural services modifier reports work above and beyond the norm when the operative note describes extensive circumstances and no other code fits. It is a procedure modifier and is never appended to an E/M code; extended E/M work is handled through time and prolonged service codes instead.
Example: An unusually long office evaluation is addressed through documented total time and prolonged service reporting, not by appending the increased-procedural-services modifier to the visit code.
Mistake to avoid: Attaching the increased procedural services modifier to an E/M code to capture extra visit work.
Reference: AAPC CEMC study guide sample
36. Payer regulation of the leveling method
Although CPT permits selecting MDM or total time case by case, payers may have regulations on when each method is used. Unless a case or question specifically states Medicare covers the patient, CPT guidelines govern the selection, and Medicare status should never be assumed from the patient's age.
Example: A commercial payer following Medicare rules is stated in the note; otherwise the coder applies CPT E/M guidelines without importing payer-specific restrictions.
Mistake to avoid: Assuming Medicare coverage from age and applying payer policy the scenario never states.
Reference: AAPC CEMC study guide sample
Modifier Application in Practice
37. Significant, separately identifiable E/M on a procedure day
Modifier 25 is appended to the E/M code when a significant, separately identifiable E/M service occurs on the same day as a minor procedure with zero to ten global days or an xxx-global service. A separate diagnosis is not required, but documentation must show work beyond what normally accompanies the procedure.
Example: A patient presenting for a scheduled injection who also receives evaluation and management of a new complaint may have the visit coded with modifier 25 when the note supports separate, significant work.
Mistake to avoid: Appending modifier 25 to every same-day visit without documentation of distinct, significant E/M work.
Reference: AAPC CEMC study guide sample
38. Unrelated E/M during a postoperative period
Modifier 24 identifies an E/M service by the same professional during a postoperative period that is unrelated to the procedure. A different diagnosis is necessary to show the visit falls outside the surgical package, and non-Medicare payers may accept it for visits due to complications of the earlier procedure.
Example: A patient in a global period presenting with a new, unrelated problem has that visit coded with modifier 24 and the new diagnosis supporting the unrelated nature of the service.
Mistake to avoid: Reporting a routine postoperative check as an unrelated E/M with modifier 24.
Reference: AAPC CEMC study guide sample
39. Decision for major surgery modifier
Modifier 57 is appended to the E/M code when the decision for major surgery is made on the day of surgery or the day before. It attaches to the E/M, not the surgical code, and it is not used for minor surgery, where modifier 25 is the appropriate choice for a separately identifiable visit.
Example: An office evaluation on the day before a major operation, at which the decision to operate is made, reports the visit with modifier 57 on the E/M code.
Mistake to avoid: Appending the decision-for-surgery modifier to the surgical code or using it for same-day minor procedures.
Reference: AAPC CEMC study guide sample
40. Professional component reporting
Modifier 26 reports the professional component of a diagnostic service that includes both technical and professional parts, representing the physician's interpretation and report. The interpretation must be documented and cannot consist solely of computerized results; it may be part of the final report but must exist.
Example: A physician who only interprets an X-ray taken at a facility reports the radiology code with modifier 26, supported by a documented interpretation and report.
Mistake to avoid: Billing the professional component from a computer-generated result with no physician interpretation documented.
Reference: AAPC CEMC study guide sample
41. Technical component and the global service
The technical component, reported with modifier TC, covers the technician's work, equipment, and supplies, and normally accounts for the larger share of reimbursement. When both components are performed in the provider's office, the radiology code is reported without either modifier as a global service.
Example: An in-office X-ray performed and interpreted by the practice is billed globally with no modifier, while the same study performed at a hospital splits into professional and technical component claims.
Mistake to avoid: Splitting a wholly in-office diagnostic service into professional and technical component claims.
Reference: AAPC CEMC study guide sample
42. Multiple procedures modifier
Modifier 51 is a procedure modifier, not applicable to E/M services, and some payers require it on the code describing the second and subsequent same-day procedures. Because requirements vary, confirm whether the payer expects it appended or applies its own multiple-procedure logic internally.
Example: A patient undergoing two separately reportable minor procedures on one date may carry modifier 51 on the second procedure code where the payer requires it.
Mistake to avoid: Appending the multiple-procedures modifier to an E/M code or to the first-listed procedure of the day.
Reference: AAPC CEMC study guide sample
Physician, NPP, and Payer Billing Rules
43. Incident-to billing under the physician identifier
Incident-to services are performed by non-physician practitioners such as physician assistants, advanced registered nurse practitioners, and certified nurse midwives, and are billed under the physician's national provider identifier. The arrangement allows qualifying clinical staff services to be reported under physician billing when requirements are met.
Example: A physician assistant treating an established patient within the physician's existing treatment plan has the service billed under the physician's identifier under incident-to rules.
Mistake to avoid: Reporting a service under the physician's identifier when incident-to requirements are unmet.
Reference: AAPC CEMC study guide sample
44. New problems break incident-to billing
A new problem does not fall under the physician's existing treatment plan because it is the first instance of that problem. In such cases the service is billed by the non-physician practitioner rather than under the physician's identifier, distinguishing established-plan follow-up from genuinely new evaluations.
Example: An established patient presenting with a first-time complaint to the NPP is billed under the NPP's identifier because no existing treatment plan covers the new problem.
Mistake to avoid: Billing a brand-new problem visit under the physician's identifier as though it were routine follow-up.
Reference: AAPC CEMC study guide sample
45. Split and shared visits in facility settings
A shared or split visit occurs when an NPP and physician are involved in the same patient case. Per CMS, these do not apply in the office setting, where incident-to requirements govern instead; in the facility setting, the service is billed by whichever professional performs the substantive portion, meaning more than half of the visit.
Example: A hospital encounter where the physician performs most of the face-to-face work is billed by the physician; the identical arrangement in the office follows incident-to rules instead.
Mistake to avoid: Applying split-shared billing logic to an office encounter, where it does not apply.
Reference: AAPC CEMC study guide sample
46. Three required consultation elements
Under CPT, a consultation requires a request from a physician or qualified source, documentation of that request, and a written report sent back to the requesting provider. If any element is missing, such as the absence of a written report, the service cannot be billed as a consultation.
Example: A specialist who evaluates a referred patient and sends recommendations back to the requester meets consultation criteria; the same visit without the return report does not.
Mistake to avoid: Billing a consultation when the written report back to the requesting provider was never sent.
Reference: AAPC CEMC study guide sample
47. Medicare policy on consultation codes
CMS no longer reimburses consultation codes, so when documentation indicates the patient is covered by Medicare, office or outpatient E/M codes or hospital care codes must be used instead. Medicare status must be stated in the case note or question, never inferred from the patient's age.
Example: A Medicare patient seen in consultation is reported with the appropriate office or hospital E/M code rather than a consultation code, because Medicare does not reimburse them.
Mistake to avoid: Reporting consultation codes for a Medicare patient or assuming Medicare coverage from age alone.
Reference: AAPC CEMC study guide sample
48. CPT guidelines as the default rulebook
Individual payer rules are not a consideration in choosing the right answer unless the case note or question specifically states Medicare covers the patient; otherwise CPT coding guidelines govern. This keeps physician and qualified-healthcare-professional coding decisions anchored to the code book rather than to payer assumptions.
Example: A question silent on payer is answered by CPT E/M guidelines, not by a Medicare-specific billing restriction the scenario never invoked.
Mistake to avoid: Importing an unstated payer policy into a scenario that only supports CPT guidelines.
Reference: AAPC CEMC study guide sample
Procedures, Diagnostics, and Code Sets
49. Sequencing multiple procedures
When multiple procedures are performed, CPT codes are sequenced with the most complex or labor-intensive procedure first, which corresponds to the codes carrying the highest relative value units. Correct sequencing matters for the payment hierarchy and for orderly claim review across the encounter.
Example: A date involving a complex injection and a simple lesion removal lists the higher-value injection code first, followed by the lesser procedure.
Mistake to avoid: Sequencing procedure codes by the order the services appear in the note.
Reference: AAPC CEMC study guide sample
50. Skin tag removal by lesion count
Removal of multiple fibrocutaneous skin tags is coded by the total number of lesions removed: the base code covers up to and including fifteen lesions, and an add-on code reports each additional ten lesions beyond that. The lesion count must be established before any code is selected.
Example: A patient with twenty-three skin tags removed reports the base code plus one add-on unit for the ten lesions beyond the first fifteen.
Mistake to avoid: Coding each lesion separately instead of using the count-based base and add-on structure.
Reference: AAPC CEMC study guide sample
51. Complication codes without the word complication
A complication code may be assigned when the documentation shows a condition altered the course of the surgery or other care, even if the provider never writes the word complication; the operative report's description of the altered course supplies the link between the condition and the care. When that relationship is unclear, the provider is queried rather than the coder assuming a complication.
Example: An operative report describes unexpected findings that forced the surgeon to change the planned approach mid-procedure; the complication code is assignable even though the word complication never appears, because the condition altered the course of the surgery as documented in the report.
Mistake to avoid: Waiting for the literal word complication when the altered course of care is already documented, or assigning a complication code from a coexisting condition that never altered the course of care.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
52. Radiology documentation requirements
Radiology documentation must include the ordering diagnosis and the number of views obtained. The ordering diagnosis establishes medical necessity for the study, and the view count drives the specific code selection within the radiology subsection; without both elements the study cannot be accurately coded or supported.
Example: A two-view chest study ordered for a documented cough is coded to the two-view chest code with the cough supporting necessity; a missing view count blocks selection.
Mistake to avoid: Coding a radiology study without documenting the number of views or the ordering diagnosis.
Reference: AAPC CEMC study guide sample
53. CPT code categories and their purposes
Category I five-digit numeric codes make up the bulk of CPT, Category II codes ending in F are supplemental tracking codes, and Category III codes ending in T describe emerging technologies. Both supplemental categories have grown, and modifiers may be appended to Category I and Category III codes.
Example: A practice reporting an emerging-technology service selects the four-digit T-suffixed Category III code rather than forcing an analogous Category I code.
Mistake to avoid: Confusing supplemental Category II tracking codes with billable Category I procedure codes.
Reference: AAPC CEMC study guide sample
54. HCPCS Level II structure and updates
HCPCS Level II codes, one alphabetic character followed by four digits, include permanent national codes updated once per year and temporary national codes with an initial Q or F character updated mid-year and again at year-end. Level III local codes were largely eliminated when HIPAA mandated a universal code set.
Example: A temporary national code identified by its initial Q character signals a mid-year-updated HCPCS entry rather than a permanent code revised only annually.
Mistake to avoid: Treating a temporary Q or F code as a permanent national code with annual-only updates.
Reference: AAPC CEMC study guide sample
HIPAA Privacy and Professional Compliance
55. Who is a covered entity
The Privacy Rule applies to health plans, health care clearinghouses, and health care providers who transmit health information electronically in connection with standard HIPAA transactions such as claims and eligibility inquiries. A provider using email alone is not covered; the transmission must involve a standard transaction.
Example: A small physician practice submitting electronic claims is a covered entity, while a practice communicating only by email without standard transactions may fall outside coverage.
Mistake to avoid: Assuming any provider using email or computers is automatically a covered entity.
Reference: HHS Summary of the HIPAA Privacy Rule
56. Business associate agreements
A business associate is a non-workforce person or organization performing functions for a covered entity involving protected health information, such as claims processing, billing, or auditing. A written agreement must impose safeguards, and the associate's authorized employees may access the PHI provided for review while following all HIPAA regulations.
Example: An outside coding audit company signing a business associate agreement may receive practice records for review, with its authorized staff bound by the same privacy obligations.
Mistake to avoid: Releasing records to an external auditor without a signed business associate agreement in place.
Reference: AAPC CEMC study guide sample; HHS Summary of the HIPAA Privacy Rule
57. Protected health information and de-identification
Protected health information is individually identifiable health information in any form, whether electronic, paper, or oral, relating to health, care, or payment that identifies the individual. De-identified information, achieved by removing specified identifiers or by formal statistical determination, carries no use or disclosure restrictions.
Example: A dataset stripped of names, addresses, and other listed identifiers, with no knowledge it could re-identify anyone, may be used freely for internal analysis.
Mistake to avoid: Treating a record with names and dates removed as de-identified while other listed identifiers remain.
Reference: HHS Summary of the HIPAA Privacy Rule
58. The minimum necessary standard
Covered entities must make reasonable efforts to use, disclose, and request only the minimum protected health information needed for the intended purpose, and may not send an entire medical record unless specifically justified. The standard does not apply to treatment disclosures, disclosures to the individual, or authorized uses.
Example: A payer request for one visit's documentation is answered with that encounter's records, not the patient's complete chart, because the purpose is payment for that visit.
Mistake to avoid: Routinely releasing the entire chart when the request only requires a specific encounter's records.
Reference: HHS Summary of the HIPAA Privacy Rule
59. Permitted versus authorized disclosures
Uses and disclosures for treatment, payment, and health care operations are permitted without individual authorization, while marketing communications and most uses of psychotherapy notes require written authorization. Authorizations must be in plain language, specify the information and parties, and state expiration and revocation rights.
Example: Sending records to a consulting physician for treatment needs no authorization, but disclosing results to a pharmaceutical firm for its marketing requires one.
Mistake to avoid: Releasing psychotherapy notes or marketing-related PHI under the treatment, payment, and operations permission.
Reference: HHS Summary of the HIPAA Privacy Rule
60. Individual rights over their records
Individuals may access and copy their protected health information in the designated record set, request amendment of inaccurate information, and obtain an accounting of disclosures, which excludes treatment, payment, operations, and authorized disclosures. Providers must make a good-faith effort to obtain acknowledgment of the privacy practices notice.
Example: A patient's request for an accounting receives the disclosures outside treatment, payment, and operations within the permitted lookback, not a list of routine claims submissions.
Mistake to avoid: Treating routine treatment and payment disclosures as items that must appear in a disclosure accounting.
Reference: HHS Summary of the HIPAA Privacy Rule
References and further reading
Source links checked on Oct 2, 2026.