6.1 OPPS and Ambulatory Payment Classifications

OPPS and Ambulatory Payment Classifications

Quick Answer: The Centers for Medicare & Medicaid Services (CMS) pays most hospital outpatient department (HOPD) services under the Hospital Outpatient Prospective Payment System (OPPS). CMS groups clinically similar services that use similar resources into Ambulatory Payment Classifications (APCs). For calendar year (CY) 2026, CMS's November 21, 2025 OPPS/ASC final rule fact sheet (CMS-1834-FC) states a 2.6% OPPS payment update for hospitals that meet applicable quality reporting, built from a 3.3% hospital market basket minus a 0.7 percentage point productivity adjustment.

This independent OpenExamPrep chapter helps learners study OPPS and APC payment for the American Academy of Professional Coders (AAPC) Certified Outpatient Coder (COC) exam. It is not an AAPC or CMS product, and OpenExamPrep does not claim partnership, official review, or approval by AAPC or CMS.

Why APC logic is a facility-coder skill

AAPC's Taking the COC exam page puts payment methodologies at 13 of 100 questions and names OPPS and IPPS in that domain. A coder who can assign Current Procedural Terminology (CPT) for a laparoscopic cholecystectomy still misses payment items if the coder cannot explain how that CPT maps to an APC, why a clinic visit and a packaged supply do not each generate their own check, or why a hospital that skipped Hospital Outpatient Quality Reporting (OQR) data receives a smaller update.

Professional-fee thinking does not transfer. Under the Medicare Physician Fee Schedule, one CPT often produces one professional payment. Under OPPS, one encounter can produce several APC payments, some lines package, some lines pay under a different fee schedule, and the Integrated Outpatient Code Editor (I/OCE) — not the coder's spreadsheet — applies the packaging and discounting rules after the claim is coded.

What OPPS is, and who it pays

CMS's MLN Medicare Payment Systems booklet describes OPPS under section 1833(t) of the Social Security Act. OPPS pays hospitals and community mental health centers for designated outpatient services. Medicare Claims Processing Manual, Chapter 4, is the claims-processing companion.

The same MLN booklet lists settings not paid under OPPS, including:

• Critical access hospitals (CAHs)
• Indian Health Service and Tribal hospitals
• Hospitals in American Samoa, Guam, the Commonwealth of the Northern Mariana Islands, and the U.S. Virgin Islands
• Rural emergency hospitals
• Certain off-campus provider-based departments paid under the Physician Fee Schedule
• Maryland hospitals paid under the state's cost-containment waiver

CMS also excludes some outpatient services from OPPS even when the hospital is an OPPS hospital. Classic examples in the MLN booklet are outpatient therapy and screening and diagnostic mammography, which other fee schedules pay.

If the COC item describes a CAH outpatient claim, do not force an APC story onto it. If the item describes a subsection (d) hospital's Type of Bill 13X claim, OPPS is the payment system unless a listed exclusion applies.

Ambulatory Payment Classifications

CMS assigns items and services paid under OPPS to APCs. An APC groups services that are similar clinically and in resource use. Each separately payable APC has a relative weight and a national unadjusted payment rate. The hospital may receive multiple APC payments for services on a single day. CMS discounts multiple surgical procedures performed on the same day when the status indicator calls for that reduction — section 6.2 covers status indicator T in detail.

CMS's MLN booklet lists categories that often pay separately, including many surgical, diagnostic, and non-surgical therapeutic procedures; blood and blood products; most clinic and emergency department visits; some drugs, biologicals, and radiopharmaceuticals; brachytherapy sources; corneal tissue acquisition; and certain preventive services including vaccine administration. Packaged items still appear on the claim. Packaging is not a license to omit HCPCS or charges. CMS's January 2026 OPPS update (MM14361 / CR 14361) reminds hospitals to charge for all services provided even when payment is packaged.

New Technology APCs exist when a new service cannot be reported with an existing procedure code assigned to a clinical APC and cannot yet sit in a clinical APC. Those lines still have a status indicator and a payment rate in Addendum A/B; they are not "unlisted, therefore unpaid."

Building the APC dollar amount

CMS determines separately payable medical and surgical rates by multiplying the clinical APC's scaled relative weight by a conversion factor (CF) to produce a national unadjusted APC payment rate. The relative weight measures resource need from the APC's geometric mean cost.

Geographic adjustment comes next. CMS wage-adjusts 60% of the national unadjusted rate (the labor portion) using the hospital wage index for the payment area and leaves 40% unadjusted. For CY 2026, CMS uses the Inpatient Prospective Payment System (IPPS) post-reclassified wage index for urban and rural areas for both the OPPS payment rate and the standardized copayment. Most beneficiary copayments are 20% of the APC payment rate.

MM14361 adds two copayment caps facility staff actually use at the desk: copayment amounts are limited to a maximum of 40% of the APC payment rate, and they cannot exceed the CY 2026 inpatient deductible of $1,736.

Additional OPPS payments, from the same MLN booklet, include:

• Transitional pass-through payments for qualifying drugs, biologicals, and devices that are too new for full ratesetting data
• Outlier payments when an individual service costs far more than its APC rate
• Transitional outpatient payments and a cancer-hospital adjustment for specified hospitals
• A 7.1% rural adjustment for most services at rural sole community hospitals, including essential access community hospitals in rural areas (MM14361 confirms that increase continues for CY 2026, with listed exclusions such as drugs, biologicals, cost-paid items, and pass-through items)

Outlier logic for CY 2026, per MM14361: the multiple threshold remains 1.75. The fixed-dollar threshold is $6,225. If cost exceeds both the APC times 1.75 and the APC plus $6,225, the outlier payment is 50% of estimated cost minus 1.75 times the APC payment.

The CY 2026 update, quality reporting, and the 340B offset

CMS-1834-FC is the policy document for the year. Three numbers travel together on COC items:

Hospitals that enrolled in Medicare after January 1, 2018 are excluded from that 340B offset. CMS estimated the 0.5% reduction would continue until aggregate recovery reached $7.8 billion of increased non-drug payments from CY 2018–2022 (CMS had estimated CY 2041). After comments, CMS kept 0.5% for CY 2026 rather than accelerating to 2%.

Do not confuse the OQR 2-percentage-point reduction with the 340B 0.5% offset. One is a quality-reporting penalty on the annual update. The other is a conversion-factor remedy on non-drug items. A hospital can be subject to both, one, or neither.

CMS also continued the hospital market basket as the ASC update factor through CY 2026 while it studies migration of outpatient surgery from HOPD to ASC.

Off-campus clinic and drug-administration payment

CMS has, since CY 2019, paid many clinic visits in excepted off-campus provider-based departments at a Physician Fee Schedule–equivalent rate to control volume. For CY 2026, CMS-1834-FC expands that method to drug administration services in excepted off-campus departments: HCPCS assigned to drug-administration APCs 5691–5694, billed with modifier PO, pay at the PFS-equivalent rate. CMS estimated $290 million lower OPPS spending from that provision ($220 million Medicare, $70 million beneficiary coinsurance). A COC item that names an excepted off-campus infusion chair is testing site-of-service payment, not CPT hierarchy alone.

Candidate scenario: same CPT, two different checks

Jordan abstracts for a 250-bed subsection (d) hospital. Two Medicare patients receive the same separately payable outpatient procedure on the same day, coded with the same CPT, mapped to the same clinical APC.

Patient A's hospital submitted complete OQR data. Patient B's hospital — a neighboring facility whose quality-file flag is blank — did not. MM14361 tells the Pricer to apply a reduced update ratio of 0.9805 to payment and copayment for the hospital that failed reporting or failed validation. Jordan's coder friends want to "fix" Patient B's payment by changing the CPT. That is the wrong lever. The HCPCS and APC can be identical; the provider-specific file carries the quality indicator that changes the conversion-factor path.

Jordan also checks whether the service is a non-drug item subject to the 0.5% 340B offset. If it is, and the hospital is not a post-January 1, 2018 enrollee exception, MM14361 applies 0.9951 to that non-drug payment. Confusing that offset with the OQR reduction produces a wrong COC answer even when the APC assignment is perfect.

What to recheck on CMS pages

Rates and addenda update quarterly. Recheck the source, not a screenshot:

• CY 2026 OPPS/ASC final rule fact sheet (CMS-1834-FC)
• MLN Medicare Payment Systems
• MM14361 January 2026 OPPS update