A federal audit has found that UnitedHealthcare, the country’s largest health insurance company by revenue, likely inflated its Medicare billing claims by at least $46.9 million between 2020 and 2021.

The Medicare compliance review, conducted by the U.S. Department of Health and Human Services’s inspector general’s office, concluded that UnitedHealthcare upcoded various diagnoses during the 2020-21 payment period, including when it billed for strokes, embolisms, and several different types of cancers.