A Wisconsin bookkeeper who worked at a nursing home for 31 years is suspected of garnering $850,000 in what authorities describe as a complex embezzlement scheme.

Joyce Ziehli, 55, who worked at New Glarus Home in New Glarus, WI, is facing six charges of felony theft. In an audit, a local accounting firm said it found 31 separate misappropriations over two months, resulting in $42,776 transferred out of the home’s residential account, the Wisconsin State Journal reported. A follow-up report that went back to January 2003 said Ziehli issued checks payable to herself and deposited them into seven accounts at two banks. The accountant turned in an 879-page report detailing more than 600 illegal transactions over a 10-year-period, the paper reported.

According to authorities, Ziehli took checks from insurance companies that covered a portion of medical costs incurred by nursing home residents. She sometimes recorded the percentage as less than what the insurance companies sent and then took the unrecorded percentage for herself. No nursing home resident accounts were affected.

Ziehli was due back in court Feb. 6.