The 25-year-old from Salem, Oregon, had used Turbo Tax to file her income tax return for 2011.
She claimed earnings of $3million but used the tax calculator programme to claim a refund of $2.1million, Oregon Live reported.
Due to the size of the refund, her electronic claims was examined by several people within the Oregon Revenue Department.
Incredibly, they approved the payout and Reyes was sent a visa card by the tax preparation computer programme containing a balance of $2.1million.
Prosecutors said she went on a spending spree and spent more than $150,000.
She later reported the card missing, prompting an investigation which uncovered the massive fraud which is believed to be the biggest in the history of the state of Oregon.