What are CPT, ICD-10 and place-of-service codes?

Three code sets show up on nearly every claim. Each answers a different question.

CPT says what was done. It is a five digit code for the service, and it is what a charge is priced on. The classic example is 99213, a standard office visit. Related sets you will also meet are HCPCS, used for supplies, drugs and equipment, and modifiers, which are two character suffixes that qualify a code. A modifier can say “this was a separate service on the same day” or “this was the left side,” and a missing or wrong modifier is a very common denial.

ICD-10 says why it was done. It is the diagnosis: the reason for the visit, written in a code the payer understands. Payers compare the why against the what. If the diagnosis does not support the service, the claim gets denied even though the care was fine.

Place of service says where it happened. A visit in the office is place of service 11. A hospital outpatient department is a different code, and the payer prices the service differently depending on which one you send.

Get all three right and most claims sail through. Get one wrong and you meet the denial that says so.