AMT CMAS common mistakes
AMT CMAS · Understand the traps and how to avoid them.
Assigning an ICD-10-CM code from the alphabetic index without confirming it in the tabular list, so a code is reported that lacks a required 4th, 5th, or 6th character or omits an instructional note (Excludes1, Code first, Use additional code).
Candidates treat the index entry as the final answer and skip the tabular verification step, especially under time pressure, because the index 'looks complete.'
What to do instead
Adopt a fixed two-pass habit: locate the term in the index, then always open the tabular list to confirm character count, laterality, encounter type, and all instructional notes before finalizing the code.
Sequencing diagnoses in the order the patient mentioned them or the order they appear on the encounter form, rather than by the reason for the encounter and coding guidelines.
Candidates confuse 'most important to the patient' with 'first-listed/principal diagnosis' and do not re-read the guidelines on sequencing and etiology/manifestation pairs.
What to do instead
Before coding, identify the chief reason for the visit explicitly, then apply the guideline for principal/first-listed diagnosis; for 'X due to Y' conditions code the underlying condition first and the manifestation second.
Coding from a provider's documented sign, symptom, or probable/rule-out diagnosis as though it were a confirmed condition, or coding a symptom when a definitive diagnosis is documented.
Candidates either over-code (assigning the suspected condition) or under-code (billing the symptom when the provider gave a definitive diagnosis), because they are unsure of the outpatient rule on uncertain diagnoses.
What to do instead
Memorize the rule: in outpatient settings do not code probable, suspected, or rule-out conditions-code the signs/symptoms that prompted the visit instead; when a definitive diagnosis is documented, code the diagnosis, not the symptom, unless the guideline directs otherwise.
Mismatching CPT/HCPCS procedure codes to the documented service-wrong E/M level, missing modifier, or bundling an add-on code without its primary procedure.
Candidates pick codes by familiar name or habit rather than reading the code descriptor and the documentation, and they forget modifier and add-on rules under exam time limits.
What to do instead
Read each descriptor in full, match documented elements (history, exam, medical decision making, or time) to the code, and verify that every add-on code is paired with its required primary code and that modifiers are supported by the note.
Entering charges or payments without verifying patient eligibility, benefits, and network status, leading to denials, wrong copay collection, or balance billing of a managed-care member.
Candidates treat insurance verification as a back-office afterthought and do not connect eligibility/benefit checks to reimbursement outcomes or to contractual prohibitions on balance billing.
What to do instead
Follow a front-end routine: confirm eligibility and benefits before the visit, document the verification, collect the correct copay/coinsurance per plan terms, and never bill a managed-care member beyond contractual patient responsibility.
Reporting a claim with mismatched patient identifiers or demographics (name spelling, date of birth, member ID, or payer) that do not match the insurance record.
Candidates copy from memory or from a stale source instead of the current insurance card and registration, and they skip a demographic cross-check before submission.
What to do instead
Build a pre-submission check that compares claim demographics against the scanned insurance card and registration record; correct discrepancies at the source before the claim leaves the office.
Writing progress or encounter notes that omit required elements-chief complaint, history, exam findings, assessment, plan, or the medical necessity rationale-so the note cannot support the billed code.
Candidates document conversationally and assume the reader will infer the reasoning, rather than documenting to the standard the code and payer require.
What to do instead
Use a structured note template (chief complaint, history, exam, assessment, plan, medical necessity) and, before signing, ask whether a reviewer could justify the code from the note alone.
Using unapproved abbreviations, symbols, or paraphrased terminology in the medical record, or transcribing a dictated term without confirming its meaning.
Candidates rely on shorthand learned informally and do not check the practice's approved-abbreviation list, creating ambiguity or compliance risk.
What to do instead
Maintain and apply the practice's do-not-use abbreviation list, spell terms out when in doubt, and query the provider for any dictated term that is unclear rather than guessing.
Disclosing or discussing protected health information in an unsecured channel-hallway conversations, unencrypted email, personal devices, or social media-or releasing records without a valid authorization.
Candidates underestimate how broadly HIPAA's minimum-necessary and authorization rules apply and treat casual channels as harmless.
What to do instead
Apply minimum necessary to every disclosure, use only approved secure channels and devices, verify a valid authorization (patient, purpose, expiration, right to revoke) before releasing records, and route questions to the privacy officer.
Responding to an angry or confused patient by arguing, over-explaining, or promising an outcome (a waiver, a refund, a specific payment) that the practice cannot guarantee.
Candidates conflate being helpful with resolving the issue on the spot and lack a scripted escalation path, so they improvise under pressure.
What to do instead
Use active listening and a scripted acknowledgment, state only what you can verify, and escalate billing or clinical disputes to the appropriate staff; never commit the practice to a financial or clinical outcome you are not authorized to make.