This guide organizes sixty study concepts into ten sequenced groups, moving from diagnosis coding conventions through E/M leveling, MDM scoring, modifiers, procedures, and compliance scenarios. Work the groups in order, since later material assumes earlier distinctions. Each concept pairs a rule with a worked example and a common error, so you can resolve the example yourself before reading the decision. Use it alongside current ICD-10-CM, CPT, and HCPCS Level II code books, because concepts reference guidelines you must locate quickly. This guide teaches subject matter only; it is not an official syllabus and does not replace official preparation materials.
ICD-10-CM Conventions and Code Book Navigation
1. Verify Every Code from Index to Tabular List
Begin with the main term in the Alphabetic Index, follow all cross-references and see-also entries, then confirm the code in the Tabular List while reading footnotes, disease definitions, and instructional notes. The Index alone never establishes the final code assignment.
Example: An index search for upper respiratory infection leads to J06.9; the tabular entry confirms no conflicting note, so J06.9 is reported because it was verified.
Mistake to avoid: Assigning a code directly from the Alphabetic Index without checking Tabular List instructions.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
2. Use the Placeholder Character X Correctly
When a code family requires a seventh character but the code itself has fewer characters, fill the open positions with the placeholder X so the code reaches the required length. This convention appears in injury, poisoning, and fracture families where episode-of-care extensions are mandatory.
Example: A subsequent-episode ankle sprain requires placeholder X characters in the empty positions before the seventh character identifying a subsequent episode of care.
Mistake to avoid: Dropping placeholder X and submitting a code with the wrong number of characters.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
3. Apply Seventh Characters for Episode of Care
Fracture and injury codes often require a seventh character identifying initial, subsequent, or sequela episode, supported by earlier characters for site, laterality, and displacement. If documentation omits any required element, correct selection is impossible and the provider should be queried.
Example: A hand fracture note lacks displacement status, so the coder cannot build the required character set and queries the provider rather than guessing an episode value.
Mistake to avoid: Assigning a seventh character when laterality or displacement is not documented by the provider.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
4. Distinguish Excludes1 from Excludes2 Notes
An Excludes1 note means the excluded condition can never be reported with that code because the two are mutually exclusive. An Excludes2 note means the condition is not included at that code but may still be coded separately when both conditions are documented and supported.
Example: A code carrying an Excludes1 note for a concurrent condition means only one of the two codes is reported, while an Excludes2 note permits both when each is documented.
Mistake to avoid: Reporting both conditions together when an Excludes1 note prohibits that combination.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
5. Choose Between Other and Unspecified Codes
An unspecified code is appropriate when documentation does not state the detail the classification requires. An other code is appropriate when documentation supplies detail that no specific code in that family captures. Choosing unspecified when detail exists understates the encounter.
Example: A note documents a specific variant with no named code in the family, so the coder chooses the other code rather than the unspecified default because the detail is documented.
Mistake to avoid: Defaulting to unspecified codes when the record clearly documents greater clinical specificity.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
6. Follow Annual Updates and Convention Precedence
ICD-10-CM revisions take effect on the first of October each year with no grace period for transition, so current-year books are mandatory. When instructions and guidelines appear to conflict, the conventions and instructions built into the classification itself take precedence over the supplemental official guidelines.
Example: A coder using a prior-year book misses a revised code family and reports an invalid code; the current edition prevents the error because revisions apply immediately.
Mistake to avoid: Coding from an outdated code book after the annual October revision date.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
Outpatient Diagnosis Selection and Sequencing
7. Sequence the First-Listed Diagnosis from the Chief Reason
In outpatient coding, the first-listed diagnosis describes the most significant reason for the visit, generally reflecting the chief complaint. Relevant coexisting conditions and history are reported as secondary diagnoses. The provider's listing order in the note does not control the coding sequence.
Example: A visit for cough with stable hypertension also noted reports the respiratory diagnosis first because it occasioned the encounter, regardless of the note's list order.
Mistake to avoid: Copying the provider's diagnostic list order without applying the outpatient sequencing rules.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
8. Separate Outpatient Rules from Inpatient Principal Diagnosis
Section IV of the official guidelines governs outpatient reporting, where first-listed diagnosis logic applies. Sections II and III use the UHDDS principal diagnosis concept, defined as the condition established after study to be chiefly responsible for occasioning the admission. E/M coders work from Section IV.
Example: The same pneumonia is first-listed at a clinic visit but becomes a principal diagnosis only after inpatient study establishes it as the reason for admission.
Mistake to avoid: Applying inpatient principal-diagnosis definitions drawn from the UHDDS to routine office encounter claims.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
9. Report Chronic Conditions Only When Addressed
Many patients carry numerous chronic complaints, but a chronic condition is reported only when it is treated at the encounter or becomes an active factor in the patient's care. A condition merely listed in the history without current relevance to management is omitted from the claim.
Example: Hypertension appears in the past history but is not assessed or managed today, so no hypertension code is reported for this visit because it was not addressed.
Mistake to avoid: Reporting every chronic condition listed in the history section regardless of current relevance.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
10. Code Coexisting Conditions That Affect Care
Code all documented conditions that coexist at the time of the encounter and that require or affect patient care, treatment, or management. Do not code conditions that were previously treated and no longer exist, since diagnoses relating to earlier episodes without current bearing are excluded.
Example: Diabetes that complicates today's wound management is reported as a secondary diagnosis, while a resolved appendectomy from years ago is not because it no longer exists.
Mistake to avoid: Reporting previously treated and resolved conditions as current diagnoses on today's claim.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
11. Use History Codes as Secondary Support
Categories Z80 through Z87 identify personal and family history. These history codes are assigned as secondary codes when the historical condition has an impact on current care or influences treatment decisions, such as guiding screening intensity or medication selection at the encounter.
Example: A mother's breast cancer history drives today's enhanced screening discussion, so the family history code supports the encounter as a secondary diagnosis because it influenced care.
Mistake to avoid: Sequencing a history code first when a current reason for the encounter exists.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
12. Report the Postoperative Diagnosis When It Differs
For ambulatory surgery, code the diagnosis for which the surgery was performed. When the postoperative diagnosis is known to differ from the preoperative diagnosis at the time the diagnosis is confirmed, select the postoperative diagnosis for coding because it is the most definitive finding.
Example: A lump excised as a suspected cyst proves to be a lipoma on final pathology, so the lipoma code replaces the preoperative cyst code because it is definitive.
Mistake to avoid: Reporting the preoperative diagnosis when final pathology establishes a different definitive finding.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
Diagnostic Certainty, Symptoms, and Test Results
13. Never Code Uncertain Outpatient Diagnoses
Terms such as probable, suspected, questionable, rule out, consistent with, and working diagnosis indicate uncertainty and are not coded in outpatient settings. Instead, code the highest degree of certainty known for that encounter, such as symptoms, signs, or abnormal test results.
Example: A provider documents suspected lymphoma in a patient with new neck lymphadenopathy, so the encounter is coded to the enlarged lymph nodes rather than to malignancy, because no biopsy has confirmed the diagnosis.
Mistake to avoid: Reporting a suspected malignancy before any confirmatory testing establishes the actual diagnosis.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
14. Separate Integral Symptoms from Unrelated Ones
Signs and symptoms integral to a confirmed definitive diagnosis are not reported separately. Additional symptoms are coded only when they are not integral to the disease process, such as when the provider documents reason to believe a symptom stems from an unrelated condition.
Example: A patient with confirmed diverticulitis also reports back pain that the provider documents as mechanical and unrelated to the intestinal disease, so the back pain code is reported alongside the diverticulitis because the symptom is not integral to that diagnosis.
Mistake to avoid: Coding every symptom listed in the note alongside an established definitive diagnosis.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
15. Use Test Interpretations to Reach Definitive Codes
For outpatient diagnostic tests interpreted by a physician with the final report available at the time of coding, report any confirmed or definitive diagnosis documented in the interpretation. For tests interpreted as normal, code the condition, symptom, or sign that necessitated the study instead.
Example: An office chest X-ray interpreted as acute pneumonia establishes the pneumonia code for that encounter, whereas the same study read as normal would have left the cough code in place that necessitated the imaging.
Mistake to avoid: Keeping symptom codes after a definitive positive test result establishes the diagnosis.
Reference: AAPC CEMC study guide sample
16. Code Borderline Diagnoses as Confirmed
A borderline diagnosis documented by the provider is coded as confirmed unless the classification provides a specific entry for that borderline condition, such as borderline diabetes. This rule applies regardless of care setting, and unclear documentation regarding a borderline condition should trigger a provider query.
Example: A note documenting borderline hypertension with no specific classification entry is coded as the confirmed hypertension condition today because borderline is not uncertain.
Mistake to avoid: Treating documented borderline conditions as uncertain and coding only the presenting symptoms.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
17. Distinguish Exposure from Confirmed Illness
Screening encounters use screening Z codes, and symptomatic patients without a definitive diagnosis receive symptom codes, with an exposure code added when actual or suspected contact is documented. An asymptomatic person with a positive laboratory result requires a provider query because false positives are possible.
Example: A symptomatic patient with documented COVID-19 exposure receives cough and fever codes plus the exposure code, since no definitive illness diagnosis is established.
Mistake to avoid: Assigning the illness code based only on exposure history or an unconfirmed positive test.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
18. Let Each Date of Service Stand Alone
Every diagnosis assigned must be supported by documentation linked to that specific claim, because individual dates of service must stand alone. Coders must not assume or extrapolate information from the record, and coding a condition as acute when the note does not say so is a classic extrapolation error.
Example: A note says back pain without characterizing onset, so the coder reports the unspecified pain code rather than assuming an acute time frame not documented.
Mistake to avoid: Inferring acuity, laterality, or severity that the current note never documents.
Reference: AAPC CEMC study guide sample
Advanced Diagnosis Rules: Sequela, Pain, Neoplasm, Z Codes
19. Sequence Acute Over Chronic When Both Exist
When a condition is documented as both acute or subacute and chronic, and a single code does not describe the combination, the acute or subacute code is sequenced as first-listed with the chronic code reported secondary. The provider's documentation determines which phase applies at the encounter.
Example: A flare of a long-standing condition documented as acute on chronic is reported with the acute code first and the chronic code second because no single code captures both.
Mistake to avoid: Sequencing the chronic code first when an acute exacerbation is clearly documented.
Reference: AAPC CEMC study guide sample
20. Report Sequela Without Time Limits
Sequela, or late effects, have no time limit within which they must occur. Sequela codes are usually reported as secondary diagnoses, with the effect or reason for the visit primary. Cerebrovascular late effects fall in category I69, which may accompany current stroke codes when old deficits persist.
Example: A patient with residual weakness from an old stroke presents for management of that deficit, so the late-effect code supports the visit because no time limit applies.
Mistake to avoid: Applying an arbitrary time window to decide whether a late effect still applies.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
21. Apply Category G89 Pain Coding Rules
Category G89 codes add detail such as acute, chronic, or neoplasm-related pain. Do not assign a G89 code when the underlying definitive diagnosis is known unless the encounter is for pain control or management. When used with site-specific pain codes, sequence G89 first only for pain-management encounters.
Example: A visit specifically for managing chronic traumatic neck pain reports the chronic pain code first, followed by the site code, because pain management occasioned the encounter.
Mistake to avoid: Adding a G89 code when the underlying diagnosis is known and the visit treats that condition.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
22. Sequence Neoplasm Codes by Treatment Focus
When treatment is directed at the primary site, the primary malignancy is first-listed. When an admission or encounter is chiefly for chemotherapy, immunotherapy, or external beam radiation, the appropriate Z51 code is first-listed with the neoplasm secondary. Treatment directed only at a secondary site makes that site first-listed.
Example: An encounter chiefly for chemotherapy infusion reports the Z51 encounter code first, with the underlying malignancy added as a secondary diagnosis because administration occasioned the visit.
Mistake to avoid: Sequencing the malignancy first when the encounter is chiefly for chemotherapy administration.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
23. Use Follow-Up Z Codes After Completed Treatment
Categories Z08, Z09, and Z39 describe follow-up examinations after completed treatment when the condition has been fully treated and no longer exists. When the main reason for an encounter is a follow-up exam with no further treatment for the condition, report the follow-up Z code as the first-listed code.
Example: A patient cured of an infection returns for a completion check, so the follow-up examination code is sequenced first because no active condition remains to report.
Mistake to avoid: Reporting the original condition as current after its treatment is fully completed.
Reference: AAPC CEMC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
24. Sequence Preoperative Evaluation Encounters
For patients receiving preoperative evaluations only, sequence a code from subcategory Z01.81, encounter for pre-procedural examinations, first. Assign the condition describing the reason for the surgery as an additional diagnosis, and also code any findings related to the preoperative evaluation itself.
Example: A healthy patient cleared for hernia repair reports the pre-procedural examination code first, with the hernia coded as the secondary diagnosis because clearance was the purpose.
Mistake to avoid: Sequencing the surgical condition first when the encounter is only a preoperative evaluation.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
E/M Documentation Foundations and Leveling Methods
25. Level Under Current Guidelines, Not Retired DGs
The 1995 and 1997 documentation guidelines were retired after the AMA revised office and outpatient code descriptions in 2021 and extended the revised framework to other E/M categories in 2023. Current leveling relies on the AMA guidelines printed in the CPT code book rather than the retired systems.
Example: A current-year encounter is leveled under the revised AMA guidelines, not by counting exam elements, because the old documentation grids no longer apply.
Mistake to avoid: Applying retired 1995 or 1997 documentation grids to current office visit leveling.
Reference: AAPC CEMC study guide sample
26. Apply the Three Documentation Principles
Three verification principles govern every E/M note: documentation must be legible to someone other than the documenting provider and staff; the date of service, patient name, and provider name must be easily demonstrated; and the note must support the nature of the visit and the medical necessity of services rendered.
Example: An otherwise complete note lacks a date of service and provider signature, so it fails verification before any leveling analysis begins.
Mistake to avoid: Leveling a visit from documentation that omits date, patient, or provider identification.
Reference: AAPC CEMC study guide sample
27. Document History and Exam Without Leveling by Them
For services under the revised guidelines, a medically appropriate history and physical examination, when performed, is included in the service. History and exam should still be documented, but they are not used in determining the code level; MDM or total time controls the selection.
Example: An extensively documented exam does not raise a visit to a higher code when the MDM supports only a lower level, because exam no longer controls leveling.
Mistake to avoid: Counting history and exam elements to select office visit levels under current guidelines.
Reference: AAPC CEMC study guide sample
28. Choose MDM or Total Time per Encounter
The provider may support the E/M level using either the level of MDM or the total time for services performed on the date of the encounter, chosen case by case. Whichever element is used, documentation should support the medical necessity of the visit, and payers may regulate which method applies.
Example: A visit with modest MDM but heavy same-day care coordination is leveled by documented total time rather than by the MDM grid, because either method is permitted.
Mistake to avoid: Mixing elements by leveling with MDM but adding undocumented time to justify a higher code.
Reference: AAPC CEMC study guide sample
29. Require Documented Total Time for Time-Based Coding
To use time as the leveling criterion or to report prolonged services, the provider must document the total time spent in patient care on the date of the encounter. Qualitative phrases about spending longer than usual do not establish the total time needed for either purpose.
Example: A note stating only that the provider spent extra time counseling an anxious patient supports neither a prolonged service add-on nor time-based leveling, because no total time spent on the date of encounter is documented anywhere.
Mistake to avoid: Reporting prolonged services from a qualitative statement about extra time spent.
Reference: AAPC CEMC study guide sample
30. Capture Prolonged Services Correctly
Prolonged service add-on codes are reported only when total time documentation supports them alongside the base E/M code. Modifier 22 is never appended to an E/M code, so extended visit time is captured through prolonged service codes rather than through increased-procedural-service modifiers.
Example: A documented total time exceeding the base code range supports the prolonged service add-on with the office visit code, not a modifier 22 variant, because modifiers never capture E/M time.
Mistake to avoid: Appending modifier 22 to an E/M code to capture extra visit time.
Reference: AAPC CEMC study guide sample
Medical Decision Making Leveling
31. Score All Three MDM Components
MDM is selected from three components: the number and complexity of problems addressed at the encounter, the amount and complexity of data to be reviewed and analyzed, and the risk of complications, morbidity, or mortality of patient management. Four MDM levels run from straightforward to high.
Example: A visit addressing one acute uncomplicated illness with limited data and prescription management combines the elements into a low overall MDM level.
Mistake to avoid: Leveling MDM from the final diagnosis alone without scoring all three components.
Reference: AAPC CEMC study guide sample
32. Count Only Problems Addressed at the Encounter
A problem counts toward MDM only when it is addressed within that encounter. A condition documented only as being treated by another provider does not count on its own; it counts only when the note shows additional assessment or care coordination beyond that bare statement.
Example: A note listing diabetes managed elsewhere adds nothing to MDM, but documented medication review and coordination with the specialist does count toward the level.
Mistake to avoid: Counting every listed chronic diagnosis toward problem complexity without evidence it was addressed.
Reference: AAPC CEMC study guide sample
33. Count Self-Limited Problems Toward MDM
A self-limited or minor problem is a short-term problem expected to resolve with minimal treatment and not expected to affect long-term health, such as a sore throat, an uncomplicated viral cold, or a bug bite with mild localized reaction. One such problem yields straightforward MDM; two yield low.
Example: A patient addressed for both pharyngitis and a mild insect bite reaction reaches low MDM because two self-limited problems were managed at the visit.
Mistake to avoid: Treating each minor symptom as a separate moderate problem to inflate the level.
Reference: AAPC CEMC study guide sample
34. Require Comorbidities to Be Addressed
Comorbidities and underlying diseases do not influence E/M levels unless they are addressed and their presence increases the data reviewed or the risk of management. Simply listing a chronic illness is insufficient; the note must show the condition was managed or contributed to the severity of the case.
Example: Documented heart failure that shaped today's medication decisions raises the risk element, while the same diagnosis merely pasted into the history does not because it was not addressed.
Mistake to avoid: Counting unaddressed comorbidities toward risk or data complexity when leveling the visit.
Reference: AAPC CEMC study guide sample
35. Apply the Data Element Counting Rules
A test counts toward the data element only when its professional interpretation is not separately billed; point-of-care tests such as rapid screens count even when the provider bills them. Reviewing results ordered at a prior encounter does not count at follow-up, because that review was included with the original order.
Example: Two rapid point-of-care tests performed in office count as data for today's MDM, while re-checking last week's imaging does not because that review accompanied the original order.
Mistake to avoid: Counting a separately billed interpretation or a prior encounter's result review as new data.
Reference: AAPC CEMC study guide sample
36. Anchor Risk to Management Decisions
Risk reflects the provider's judgment of the patient's likelihood of complications, morbidity, or mortality between the current visit and the next scheduled encounter, and it is separate from the inherent risk of the condition itself. The level is determined by the management decisions made during the encounter, and prescription drug management supports moderate risk.
Example: Starting a prescription medication at the visit supports moderate risk on the risk element, even when the illness itself is considered low severity, because management decisions drive risk.
Mistake to avoid: Rating risk from the diagnosis name rather than the management decisions documented.
Reference: AAPC CEMC study guide sample
E/M Code Families, Consultations, and Payer Context
37. Recognize the Special Role of 99211
Code 99211 describes services that typically do not require the presence of a provider, so the concept of MDM does not apply to it. It sits outside the MDM leveling grid and is selected when the encounter meets its descriptor, distinguishing it from the leveled established patient codes.
Example: A nurse visit for a documented blood pressure recheck with no provider presence maps to 99211 rather than an MDM-leveled office code, because MDM does not apply.
Mistake to avoid: Attempting to score medical decision making elements for a 99211 encounter.
Reference: AAPC CEMC study guide sample
38. Map MDM Levels Across New and Established Families
Office visit codes divide into new patient codes 99202 through 99205 and established patient codes 99212 through 99215. Each MDM level maps across the two families, so the same MDM level yields a different code depending on whether the patient is new or established.
Example: Low MDM maps to 99213 for an established patient; the identical MDM maps to 99203 when the patient is new to the practice, because the families differ.
Mistake to avoid: Selecting an established patient code for a new patient encounter or the reverse.
Reference: AAPC CEMC study guide sample
39. Verify All Three Consultation Elements
Under CPT guidelines, a consultation requires three components: 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, the service cannot be billed as a consultation.
Example: A specialist evaluates a referred patient but sends no report to the requester, so the service is coded as a standard visit instead because one element is missing.
Mistake to avoid: Billing consultation codes when the written report back to the requester is absent.
Reference: AAPC CEMC study guide sample
40. Replace Consultation Codes for Medicare Patients
CMS no longer reimburses consultation codes, so when documentation indicates Medicare covers the patient, office and outpatient E/M codes or hospital care codes are used instead. Never assume Medicare coverage from patient age alone; exam scenarios state Medicare status explicitly in the case note or question.
Example: A case note stating the patient is covered by Medicare leads to an office visit code rather than a consultation code, because Medicare does not pay consultation codes.
Mistake to avoid: Assuming Medicare coverage from a beneficiary's age without a stated payer in the note.
Reference: AAPC CEMC study guide sample
41. Default to CPT Guidelines Unless Medicare Is Stated
The CEMC examination tests coding concepts, anatomic principles, and coding guidelines only, not individual payer rules. Unless it is specifically stated in the case note or question that Medicare covers the patient, follow the CPT coding guidelines when selecting the answer.
Example: A commercially insured patient scenario is answered under CPT consultation rules, even though a Medicare patient would be coded differently in that same case.
Mistake to avoid: Applying Medicare payment policy to exam answers when no Medicare coverage is stated.
Reference: AAPC CEMC study guide sample
42. Code General Exams with Abnormal Findings
When a general medical examination or routine child health examination produces an abnormal finding, assign the with-abnormal-findings code as first-listed, plus a secondary code for the finding. Abnormal findings include newly identified conditions or changed severity of chronic ones. Preventive encounters, including the Welcome to Medicare physical, remain distinct from problem-oriented E/M services.
Example: A routine physical reveals uncontrolled hypertension, so the examination-with-abnormal-findings code is sequenced first with the hypertension code reported second on the claim.
Mistake to avoid: Coding only the routine examination without abnormal findings when a new problem is identified.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
CPT and HCPCS Structure with Procedure Coding
43. Distinguish the Three CPT Code Categories
Category I holds the familiar five-digit numeric codes making up the bulk of the book; Category II codes end in F and are supplemental tracking codes; Category III codes end in T and describe emerging technologies. Recognizing the suffix letters keeps tracking and experimental codes off claims for standard services.
Example: A four-digit code ending in T for an emerging technology is not substituted for the standard Category I procedure code describing the service actually performed.
Mistake to avoid: Reporting Category II or III codes as if they were payable Category I procedures.
Reference: AAPC CEMC study guide sample
44. Navigate HCPCS Levels and Code Types
HCPCS Level II contains alphanumeric codes, one letter followed by four digits, covering supplies, drugs, and services not found in CPT, with permanent national codes updated once per year and temporary Q or F codes updated mid-year. Level III local codes were largely eliminated under HIPAA's universal code set mandate.
Example: A supply item absent from CPT is reported with its alphanumeric Level II code rather than forcing an unlisted CPT procedure option.
Mistake to avoid: Searching CPT for supply and drug items that belong in HCPCS Level II.
Reference: AAPC CEMC study guide sample
45. Sequence Multiple Procedures by Complexity
When multiple procedures are performed at one session, sequence the CPT codes with the most complex or labor-intensive procedure first, because the codes with the highest relative value units lead the claim. This ordering convention applies whenever several procedures are reported together on one claim.
Example: A claim combining two procedures lists the higher-value, more complex procedure first rather than the chronological order of performance during the session.
Mistake to avoid: Sequencing multiple same-session procedures chronologically instead of by complexity and relative value.
Reference: AAPC CEMC study guide sample
46. Count Total Lesions for Skin Tag Removal
Skin tag removal coding depends on the total number of fibrocutaneous tags removed across any area. The base code covers up to and including fifteen lesions, and the add-on code reports each additional ten lesions beyond that count, so all lesions removed are counted before choosing codes.
Example: Removal of twenty-five skin tags in one session reports the base code plus one add-on unit covering the additional ten lesions, because the total count controls selection.
Mistake to avoid: Reporting separate removal codes per body area instead of one total lesion count.
Reference: AAPC CEMC study guide sample
47. Select Unlisted Procedure Codes When Nothing Fits
When no specific CPT code describes a procedure performed, select the appropriate unlisted procedure code from the relevant subsection rather than forcing a near-match that misstates the service. Unlisted codes depend on supporting documentation describing what was actually done.
Example: A novel technique with no specific code is reported with the unlisted code for that family rather than the closest similar listed procedure, because no code describes it.
Mistake to avoid: Substituting a similar listed procedure code when only an unlisted code applies.
Reference: AAPC CEMC study guide sample
48. Apply Global Surgical Package Concepts
Procedures carry assigned global periods during which related routine E/M services are bundled into the surgical payment. Minor procedures fall in zero to ten day global periods, while major surgeries carry longer periods; the assigned period length determines how same-day and postoperative visits are handled.
Example: A same-day visit with a minor procedure is evaluated under minor global period rules, unlike a visit following a major surgery, because the periods differ.
Mistake to avoid: Treating every postoperative visit as separately billable without checking the assigned global period.
Reference: AAPC CEMC study guide sample
Modifier Use for E/M and Procedures
49. Apply Modifier 25 for Same-Day Minor Procedures
Modifier 25 identifies a significant, separately identifiable E/M by the same provider on the same day as a minor procedure with zero to ten day or xxx global periods. A separate diagnosis is not required, but the documentation must support work beyond what normally accompanies the same-day procedure.
Example: A distinct assessment for a new complaint at a lesion removal visit supports the E/M with modifier 25 appended to the visit code, because separate work is documented.
Mistake to avoid: Appending modifier 25 to the procedure code instead of the E/M code.
Reference: AAPC CEMC study guide sample
50. Reserve Modifier 57 for Major Surgery Decisions
Modifier 57 is appended to the E/M code when the decision to perform major surgery is made on the day of surgery or the day before surgery. It is not used when the E/M occurs on the day of a minor surgery, where modifier 25 covers a separately identifiable E/M instead.
Example: A same-day visit that decides to proceed with major surgery reports the E/M with modifier 57, not with modifier 25, because the decision itself is the service.
Mistake to avoid: Using modifier 57 for an E/M performed on the day of a minor procedure.
Reference: AAPC CEMC study guide sample
51. Use Modifier 24 for Unrelated Global-Period E/M
Modifier 24 reports an unrelated E/M by the same provider during a postoperative global period. A different diagnosis is necessary to show the service is unrelated to the procedure. Non-Medicare payers may accept this modifier for visits due to complications from the previous procedure.
Example: A patient in a global period presents with a new unrelated problem, so the E/M carries modifier 24 with the new diagnosis documented, because the visit is unrelated.
Mistake to avoid: Billing a global-period E/M without modifier 24 when the problem is unrelated.
Reference: AAPC CEMC study guide sample
52. Split Professional and Technical Components Correctly
Modifier 26 reports the professional component of a diagnostic service having both technical and professional parts, requiring a physician interpretation and report, not merely computerized results. Modifier TC reports the technical component. When both occur in the provider's office, the radiology code is reported without a modifier.
Example: A physician only interprets a facility-performed X-ray, so the code carries modifier 26 while the facility separately bills the technical component.
Mistake to avoid: Appending modifier 26 when the physician's report consists only of computerized findings.
Reference: AAPC CEMC study guide sample
53. Separate Modifier 22 from Modifier 51
Modifier 22 reports a procedure substantially above and beyond the usual work when no other code describes the extensive service, and it is never appended to an E/M code. Modifier 51 flags second and subsequent same-day procedures for payers that require it, and it also does not apply to E/M services.
Example: An operative note describing unusually extensive work supports modifier 22 on the procedure code, while additional separate procedures may need modifier 51 instead.
Mistake to avoid: Attaching modifier 22 to an E/M code for extra time or complexity.
Reference: AAPC CEMC study guide sample
54. Support Modifier 59 with Documented Distinct Circumstances
Modifier 59 is defined as a distinct procedural service. Append it to a procedure code when the documentation establishes that a service which would otherwise not be separately reportable with another same-day service was performed under circumstances that make it independent. The distinct circumstance must be evident in the note itself rather than inferred from the mere presence of two codes on one claim.
Example: A same-day service pair that would normally combine into a single reportable service is reported as two services when the note documents that they were performed under distinct circumstances, supporting modifier 59 on the second service.
Mistake to avoid: Using modifier 59 as a generic bypass for bundling edits without distinct documentation.
Reference: AAPC CEMC study guide sample
Compliance and Special Billing Scenarios
55. Understand Incident-to Billing Basics
Incident-to services are performed by non-physician practitioners such as physician assistants and advanced registered nurse practitioners and are billed under the physician's national provider identifier. The encounter must satisfy incident-to requirements before it is billed under the physician rather than under the NPP.
Example: A routine follow-up managed by a nurse practitioner within the established plan is billed under the physician's identifier, because incident-to requirements are met.
Mistake to avoid: Billing NPP visits under the physician NPI without verifying incident-to requirements are satisfied.
Reference: AAPC CEMC study guide sample
56. Bill New Problems Under the NPP
When a patient presents with a new problem, the visit falls outside 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 being billed incident-to under the physician.
Example: An established patient sees the nurse practitioner for a first-time rash, so the claim goes out under the NPP's identifier, not the physician's, because the problem is new.
Mistake to avoid: Billing a new-problem NPP visit incident-to under the physician's own billing identifier.
Reference: AAPC CEMC study guide sample
57. Apply Split/Shared Visits Only in Facilities
A shared or split visit occurs when an NPP and a physician are involved in the same patient case. Per CMS, split visits do not apply in the office setting, where incident-to requirements govern instead. In facility settings, the substantive portion, meaning more than half of the visit, determines which provider bills.
Example: A hospital encounter where the physician performs more than half the visit is billed by the physician; the identical arrangement in an office is not a split visit.
Mistake to avoid: Applying facility split-visit rules to an encounter that takes place in the office setting.
Reference: AAPC CEMC study guide sample
58. Limit Disclosures to the Minimum Necessary
A covered entity must make reasonable efforts to use, disclose, and request only the minimum protected health information needed to accomplish the intended purpose, and it may not use or disclose the entire medical record for a particular purpose unless it can specifically justify the whole record as the amount reasonably needed. The standard does not apply to disclosures to a provider for treatment, disclosures to the individual, uses made pursuant to an authorization, disclosures to HHS for complaint investigation or compliance review, or uses required by law.
Example: A health plan's routine request to adjudicate a claim is answered with only the encounter documentation needed to support the billed service, while a physician colleague requesting records for treatment may receive the whole record without a minimum-necessary analysis.
Mistake to avoid: Sending an entire chart in response to a routine payment request without justifying the whole record as necessary.
Reference: HHS Summary of the HIPAA Privacy Rule
59. Require Authorization for Psychotherapy Notes
Psychotherapy notes are a mental health professional's notes analyzing the contents of a private counseling session, kept separate from the rest of the record; they exclude medication prescription and monitoring, session start and stop times, modalities and frequencies of treatment, test results, and summaries of diagnosis, functional status, treatment plan, symptoms, prognosis, and progress. A covered entity must obtain the individual's written authorization to use or disclose psychotherapy notes, with narrow exceptions such as the originator's own treatment, training programs, defending legal proceedings brought by the individual, and HHS compliance investigations.
Example: A payer requesting documentation to process an office visit claim may receive the standard record under payment permissions, but the separately maintained psychotherapy notes cannot be released for that payment purpose without the patient's written authorization.
Mistake to avoid: Releasing psychotherapy notes under the treatment and payment permissions that apply to the rest of the medical record.
Reference: HHS Summary of the HIPAA Privacy Rule
60. Execute Business Associate Agreements Before Sharing PHI
A business associate is a person or organization outside the covered entity's workforce that performs functions involving protected health information, such as an outside audit company. A signed business associate agreement lets authorized employees access the PHI provided for review, and the associate must follow all HIPAA regulations.
Example: A practice engaging an outside coding audit firm signs a business associate agreement, permitting auditors to review records because they remain bound by HIPAA.
Mistake to avoid: Releasing records to an outside auditor without a business associate agreement in place.
Reference: AAPC CEMC study guide sample; HHS Summary of the HIPAA Privacy Rule
References and further reading
Source links checked on Oct 2, 2026.