Goodsurance

Medicare Advantage

OIG Estimates 462 Million Dollars in Medicare Advantage Overpayments Tied to Unverified Stroke Diagnoses

A federal audit found that Medicare Advantage plans submitted acute stroke diagnosis codes to CMS via physician records for thousands of enrollees whose medical files contained no hospital record confirming the diagnosis, generating large estimated overpayments across the program.

By the Goodsurance editorial teamOctober 19, 2026

Federal auditors estimated that CMS made approximately 462 million dollars in net overpayments to Medicare Advantage organizations in 2021, based on acute stroke diagnosis codes that appeared on physician billing records without a matching hospital admission or outpatient record confirming the diagnosis.

Medicare Advantage plans receive monthly risk-adjusted payments from CMS. When a plan submits a higher-severity diagnosis for an enrollee, such as an acute stroke, CMS pays the plan a larger monthly amount. The Office of Inspector General identified a pattern in which some plans submitted acute stroke codes through physician data records even though the enrollee had no corresponding inpatient or outpatient hospital record for a stroke in the same year.

OIG audit: Medicare Advantage plans collected an estimated 462 million dollars in extra payments for stroke diagnoses that medical records did not support.

Auditors reviewed a random sample of 97 enrollees drawn from 240,401 Medicare Advantage enrollees whose plans had submitted such codes to CMS in 2020. For all 97 enrollees, the medical records either did not support the stroke diagnosis or could not be located.

Extrapolating from that sample, OIG estimated the program-wide overpayment for 2021 at approximately 462 million dollars.

OIG recommended that CMS implement a payment safeguard to flag cases where an acute stroke code appears on a physician data record but the enrollee has no hospital-based stroke record in the same service year. CMS agreed with the recommendation. The audit is part of a broader OIG series examining high-risk diagnosis codes in Medicare Advantage risk-adjustment submissions.

In plain words

Medicare Advantage plans are paid more by the government when a member has a serious health condition. A stroke is one of those serious conditions.

A government watchdog checked whether Medicare Advantage plans were correctly claiming that some of their members had strokes. Auditors looked at 97 patients. In all 97 cases, the medical records did not back up the stroke claim, or the records could not be found at all.

Based on those findings, the watchdog estimated that Medicare paid plans about 462 million dollars too much in just one year.

The watchdog asked the agency that runs Medicare to add a check: if a stroke code shows up in a doctor visit record but there is no hospital record of a stroke, the payment should be reviewed before it goes out. Medicare agreed to make that change.

Understand the basics first

Source: OIG
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