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Medicare Part B • Pharmacy Compliance • Drug Billing • HHS OIG

OIG Flags Medicare Outpatient Drug Coding Gaps

A new HHS OIG data brief identifies gaps in Medicare’s oversight of hospital outpatient drug billing. The review flagged 160,918 claim lines with mismatched drug and procedure codes, but did not establish that their $27.6 million in payments were improper. A nonstatistical sample confirmed coding errors. The findings give hospital pharmacy and billing teams a concrete reason to review drug-code mappings and claim controls, without creating a new regulatory requirement.

By Toby C. “Chad” Frost • October 30, 2026
1 min read

What OIG found

Posted October 28, the OIG brief analyzed April 2024 through March 2025 claims. It flagged 160,918 outpatient drug claim lines with National Drug Codes and Healthcare Common Procedure Coding System codes that did not match CMS crosswalks. OIG did not determine overpayments or underpayments for those lines, which received $27.6 million.12

Critical access and short-term acute-care hospitals billed 99 percent of flagged lines. In a nonstatistical sample of 30 lines, 24 used incorrect HCPCS codes. Eleven were paid under the outpatient prospective payment system and could have produced net improper payments of $1,304, including overpayments and underpayments.2

OIG identified missing crosswalk-matching edits and insufficient provider education. The brief makes no specific recommendations to CMS and does not announce a new billing requirement.2

Why this matters to pharmacy teams

Chad’s analysis: Hospital pharmacy and revenue teams should reconcile the administered product’s NDC with its current HCPCS mapping, including after product or labeler changes. A claim’s acceptance does not resolve whether that mapping is correct. The report supports targeted internal review, while its limited sample cannot supply a hospital-wide error rate.

Source notes

  1. Off. of Inspector Gen., U.S. Dep’t of Health & Hum. Servs., What’s New, entry for Oct. 28, 2026 (last visited Oct. 30, 2026).
  2. Off. of Inspector Gen., U.S. Dep’t of Health & Hum. Servs., Potential Vulnerabilities in CMS’s Oversight of Medicare Providers’ Billing of Selected Outpatient Drugs, OAS-25-09-090, at 3–4, 8–11 (Oct. 2026).