Core billing knowledge
Core billing knowledge
The Core billing knowledge domain tests the revenue cycle from patient registration through final payment posting. Expect items on code-set roles, claim forms, charge capture, modifiers, claim scrubbing, remittance posting, and patient responsibility calculations. The exam favors practical sequencing: what happens next, which form or code is correct, and how a dollar amount is posted.
Rules and concepts
- Revenue cycle order: registration and eligibility, coding and charge entry, claim scrub, submission, remittance posting, A/R follow-up, denial management, collections.
- ICD-10-CM explains why the service was medically necessary; CPT and HCPCS Level II describe what was done or supplied. Diagnosis codes do not replace procedure codes.
- CMS-1500 is the professional claim form; UB-04 is the institutional form. A professional claim needs NPI, TIN, place of service, diagnosis pointers, units, and charges.
- Modifiers clarify circumstances: 25 for a significant, separately identifiable E/M on the same day as a procedure; 26/TC split professional and technical components; 59 or X{EPSU} for distinct services when NCCI edits allow.
- Post payments in order: billed charge, allowed amount, contractual adjustment, deductible, coinsurance or copay, plan payment, patient responsibility. Do not apply coinsurance to the billed charge when the allowed amount is lower.
Worked example
A claim bills $300. The payer allowed $150, the patient has $50 of unmet deductible, and coinsurance is 20%. Contractual adjustment is $150 ($300 - $150). The patient pays the $50 deductible plus 20% of the remaining $100, or $20, for $70 total. The plan pays $80. If the patient instead had a $30 copay and no deductible, the plan would pay $120 and the patient $30, assuming the copay is within the allowed amount.
Traps
Applying coinsurance to charges rather than the allowed amount; posting a contractual adjustment as a denial; omitting a needed modifier and triggering an NCCI bundling denial; using UB-04 for a professional claim; confusing copay with coinsurance; and failing to reconcile ERA/EOB amounts to the patient ledger.