Dr. Mehmet Oz, who is President Donald Trump’s nominee to lead the Centers for Medicare and Medicaid Services, may have “significantly underpaid his Social Security and Medicare taxes” in recent years,

Senate Finance Committee Democratic tax staff who reviewed Mehmet Oz’s tax returns said the nominee to run the Centers for Medicare and Medicaid Services avoided paying some Medicare and Social Security taxes over three years.

The memo created by Democratic staff on the Senate Finance Committee comes as Oz is expected to face the panel on Friday for a confirmation hearing.