Prosecutors say 80-year-old Clarance Jones bought the tickets to help winners avoid taxes.
Jones submitted the tickets to the lottery as if they were his, collecting the full winnings.
He reported the winnings, but offset them with purported gambling losses and claimed he was a professional gambler.
Authorities say that from 2011 through 2017, Jones cashed thousands of tickets totaling $10.8 million.
He also pleaded guilty to filing false tax returns.
Jones could get up to eight years in federal prison at sentencing scheduled for Aug. 13.
Two men who assisted Jones have also pleaded guilty to various tax violations.
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