The preparer behind Hennepin County’s largest tax fraud case will be filing future returns from prison.

Rona Griffin, 52, pleaded guilty Friday to 17 counts of submitting hundreds of false tax documents and failing to pay her own taxes. She will be sentenced to nearly four years in prison for costing the state more than $1.6 million in tax revenue between 2009 and 2013.

“This is the biggest tax fraud case this office has ever seen,” County Attorney Mike Freeman said. “She cheated her clients, the state and falsified and manufactured documents. She made lots of money at the expense of others and by not filing taxes herself. Did she really think she would get away with this forever?”

In court Friday, Griffin, of Champlin, said nothing other than to answer questions from her lawyer and the judge with a yes or no. She acknowledged that if she stood trial and was convicted on all charges, she could receive a sentence of up to 6½ years in prison.

Almost a year ago, Griffin was charged with 53 felonies. The amount of restitution the state is seeking will be determined at her sentencing March 28. The Revenue Department has already recovered $500,000, and Griffin owes back taxes of at least $117,000.

Her sentence was doubled in length because of aggravating circumstances. Her scheme required a higher level of sophistication, she abused a position of trust, she forged church and mileage documents to cover up the fraud and sent a letter to the Department of Revenue stating that her only income was from child support and Social Security.

According to the criminal complaint, Griffin started her own business, HAH Broker Inc., out of her home before moving to Minneapolis. Her business, which she operated with her two daughters, did tax preparation and accounting.

Investigators learned that Griffin consistently lied about her clients’ charitable contributions and about business expenses that were not reimbursed. Many of them contributed nothing or just a few hundred dollars to charity. Griffin would report on their income tax forms that they contributed 10 percent of their income to charities, often to churches they never attended.

Griffin also would change her clients’ occupations. For instance, one client worked as a forklift operator in a warehouse. She changed that to sales representative and indicated that he had more than $10,000 in unreimbursed employee expenses in the form of mileage, travel and other business expenses, the complaint said.

When her clients began receiving letters from the Revenue Department that they would be audited, Griffin invited them to a meeting at her home in March 2013. She told a number of them to buy ledgers and create mileage reports to support their travel deduction.

Her company was quite profitable in the years between 2008 and 2013. Yet, she filed no tax returns for her HAH Broker business and only one individual tax return between 2010 to 2013. That lone return, in 2013, was false, showing a federally adjusted gross income of $9,237 when the Department of Revenue audit found that she made more than $150,000.

Before her long list of tax evasion charges, Griffin had accrued a lengthy criminal record dating to 2000. She has been arrested on forgery and swindle charges in Benton and Stearns counties and faced more than a dozen civil filings.

“She was just greedy,” Freeman said. “She hasn’t been sentenced yet and hasn’t had a chance to come up with an excuse. I think she was just good at it and kept going.”