Advance Beneficiary Notice (ABN) is the standard Medicare form, CMS-R-131, that physicians, providers and suppliers give an Original Medicare patient before a service Medicare is expected to deny, usually as not reasonable and necessary. The patient chooses whether to proceed and accept financial responsibility if Medicare does not pay.

CARC CO-11 means a payer denied or reduced a claim line because the diagnosis reported doesn’t fit the procedure billed, such as a knee procedure linked to a hip diagnosis or a right-side procedure billed with a left-side code. Group code CO assigns the balance to the provider rather than the patient.

CARC CO-16 means a payer couldn’t pay a claim or line because information was missing or the claim had a submission or billing error. A remittance advice remark code (RARC) names the specific problem, and the usual fix is to correct the data and resubmit rather than appeal.

CARC CO-197 means a payer denied a claim or line because a required precertification, authorization, notification or pre-treatment approval was not on file for the service billed. Group code CO assigns the balance to the provider, so the practice can’t shift it to the patient while the code reads CO.

CARC CO-4 means a payer reduced or denied a claim line because the procedure code doesn’t agree with the modifier billed with it, or because a modifier the code needs is missing or invalid. Group code CO assigns the balance to the provider, so the practice, not the patient, absorbs it.

CARC CO-50 means a payer treated a service as non-covered because it did not consider the service medically necessary. Group code CO assigns the balance to the provider, so the practice can’t bill the patient unless the payer assigns it to patient responsibility, for example after a valid Advance Beneficiary Notice in Original Medicare.

CARC CO-97 means a payer didn’t pay a service separately because it treats that service as already paid through another service or procedure it has processed. It is the usual result of NCCI bundling edits and global surgical periods, and group code CO keeps the balance with the provider.

Clean claim rate is the percentage of claims that pass all edits on the first attempt and go out without manual intervention. HFMA’s MAP Key CL-1 calculates it as the number of claims that pass edits with no manual touch divided by all claims accepted into the claims processing tool for billing in the period.

CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F) is a federal rule, released January 17, 2024, that requires Medicare Advantage, Medicaid and CHIP programs and plans, and qualified health plans on the federal Exchanges to explain denials, publish prior authorization metrics and build FHIR APIs. Most must also meet decision deadlines.

Days in A/R is the average number of days it takes a practice to turn charges into cash. It equals the accounts receivable balance divided by average daily charges (gross days) or by average daily net revenue (net days), measured over a stated period such as the most recent three months.

Denial rate is the share of claims, or of claim dollars, that payers deny. The initial denial rate measures denials on first adjudication; the final denial rate measures what is written off after appeals. HFMA’s Remittance Denial Rate divides claims denied by claims remitted, while dollar-based versions divide denied dollars by billed dollars.

Global surgical package means the group of services Medicare pays for with one surgical fee: related preoperative visits, the procedure itself, and routine postoperative care during a global period of 0, 10 or 90 days. Related visits and services inside that window aren’t billed separately unless an exception applies, usually shown with a modifier.

HCPCS G2211 is a Medicare add-on code, separately paid since January 1, 2024, that recognizes the added complexity of an office/outpatient E/M visit, and since 2026 a home or residence visit, when the practitioner is the patient’s ongoing hub for care or manages one serious or complex condition over time.

Medically Unlikely Edits (MUEs) are CMS limits on the units of service Medicare will pay for one HCPCS or CPT code billed by the same provider for the same patient on the same date of service. If a claim line or date exceeds the limit, Medicare denies all units for that code on that line or date.

Modifier 24 is the CPT modifier added to an evaluation and management (E/M) code when the surgeon, or a same-specialty physician in the same group, sees a patient during a procedure’s postoperative global period for a problem unrelated to that surgery. It tells the payer the visit is not routine postoperative care already included in the surgical payment.

Modifier 25 is the CPT modifier appended to an evaluation and management (E/M) code to show that, on the same day as a procedure, the same physician provided a significant, separately identifiable E/M service beyond the procedure’s usual pre- and post-procedure work. In orthopedics it most often appears on joint injection, casting and other minor-procedure days.

Modifier 57 is the CPT modifier added to an evaluation and management (E/M) code when that visit, on the day of or the day before a major procedure with a 90-day global period, results in the initial decision to perform the surgery. It separates the decision visit from preoperative care that is already included in the surgical payment.

Modifier 58 is the CPT modifier for a procedure performed by the same physician during another procedure’s postoperative period when the second procedure was planned at the time of the first, is more extensive than the first, or is therapy following a diagnostic procedure. Medicare pays it separately, and a new global period begins with it.

Modifier 59 and X{EPSU} modifiers means the group of modifiers that tells a payer two procedures normally bundled by an NCCI procedure-to-procedure edit were distinct: modifier 59 (distinct procedural service) and its four more specific HCPCS subsets, XE (separate encounter), XS (separate structure), XP (separate practitioner) and XU (unusual non-overlapping service).

Modifier 78 is the CPT modifier for an unplanned return to the operating or procedure room by the same physician, during a procedure’s postoperative period, for a related procedure such as treating a complication. Medicare generally pays only the intraoperative portion of the return procedure, and no new global period begins; the original one keeps running.

Modifier 79 is the CPT modifier for a procedure performed by the same physician during another procedure’s postoperative period when the new procedure is unrelated to the original surgery. Medicare pays the unrelated procedure separately, and a new global period begins with it, so its own follow-up care is then included in its payment.

Modifier KX is a HCPCS Level II modifier that attests a Medicare claim line meets the documented coverage requirements of the applicable policy. Orthopedic practices use it for outpatient therapy above the annual KX threshold ($2,480 for calendar year 2026) and for orthoses, such as knee braces, that meet DME MAC LCD criteria.

NCCI procedure-to-procedure (PTP) edits are CMS code-pair edits that stop Medicare from paying for two services that generally shouldn’t be reported together by the same provider for the same patient on the same date. When both codes are billed, the column one code pays and the column two code is denied unless an allowed modifier fits.

Net collection rate means the percentage of collectible revenue a practice actually collects. It divides payments by charges minus contractual adjustments for the same period, measured with a lag so payments can catch up. Also called the adjusted collection rate, it shows how much allowed revenue is lost to denials, underpayments and bad debt.

WISeR Model is the short name for the Wasteful and Inappropriate Service Reduction Model, a CMS Innovation Center test running January 1, 2026, through December 31, 2031. In Arizona, New Jersey, Ohio, Oklahoma, Texas and Washington, it adds prior authorization or pre-payment review, performed by technology companies, for selected Original Medicare services.