Tax preparer Guillermo Dahilig of Waialua pleaded guilty Thursday in federal court to one count of aiding and assisting in the preparation and filing of false tax returns.

Dahilig, owner and operator of Speedy Gill Services, prepared between 750 and 1,000 tax returns per year for clients from 2009 to 2016 and charged between $100 and $200 per return, according to court documents and information presented in court.

He falsified his clients’ tax returns by claiming deductions for items such as medical expenses, personal property tax, job expenses and charitable contributions that he knew were greater than the figures provided by his clients. Dahilig then filed the returns, knowing that they would generate refunds larger than his clients deserved.

In addition, from at least 2010 through 2013, Dahilig underreported the income of Speedy Gill Services on the income tax returns he prepared and filed for himself and his wife.

Dahilig’s sentencing is scheduled for July 16 before U.S. District Judge Susan Oki Mollway. He faces up to three years in prison, a fine of up to $250,000 and a period of supervised release of up to one year.

He agreed to pay restitution to the IRS in an amount determined by the court for the taxes due from fraudulent tax returns filed between tax years 2010 and 2015 for himself and his clients.