A Knoxville man was sentenced Monday to nearly four years in prison for defrauding the U.S. government of tens of thousands of dollars by filing fraudulent income tax returns.

Larry Steven Covington, Jr., 39, pleaded guilty in May 2017 and was sentenced Monday to 46 months in federal prison. The U.S. District Attorney’s Office says while serving time in state prison in 2008, Covington learned from another inmate how to file and prepare fraudulent income tax returns.

Prosecutors say Covington illegally obtained Social Security numbers and other information, mostly from other inmates, and used that information to prepare false tax returns, which he mailed to his mother, or gave the information to his mother over the phone so she could prepare the tax forms and mail them.

Some of the refunds were directly deposited by the IRS into two bank accounts created by Covington or mailed directly to Covington’s mother. His mother would then withdraw some of the money for herself and put the rest on Green Dot cards and sent them to Covington.

Prosecutors say over 550 fraudulent returns were filed between 2009 and 2015. Covington attempted to get over $905,000 in fraudulent refunds, but was only able to obtain nearly $164,000. He was ordered to pay that back in restitution as part of his sentence.