The man arrested for printing them is facing felony charges in California and in Virginia.
A counterfeit money operation has been shut down in Cupertino after the fake $20 bills were sold to customers across the country.
The manufacturing of counterfeit bills was going on inside a apartment complex on Torre Avenue in Cupertino next to some Apple offices.
The sheriff's office showed off inkjet printers, cartridges and 100 percent cotton paper, all off-the-shelf items, that were used in the operation. The fake $20 bills were printed in layers, showing some level of sophistication. But to the naked eye, the counterfeit bills might be difficult to detect.
Eric Aspden, 43, is facing five felony counts of selling the counterfeits, mostly through government mail.
"Mr. Aspden alone was responsible for the shipment of upwards of 2,000 packages a year of counterfeit currency linked to 30 different states and likely hundreds of thousands of dollars of counterfeit currency being flooded into our economy," said Santa Clara County sheriff's detective Justin Harper.
Sheriff's detectives believe Aspden was making over $100,000 a year from the operation.
The link to Cupertino was made by police in Fairfax County in northern Virginia where merchants were seeing a high volume of the fake $20 bills.
Because some bills were purchased in California, the counterfeits might be in local circulation.
"If you try to pass it, there's a tremendous risk. If you get caught, you're going to get charged with a crime," said Capt. Dan Rodriguez of the Santa Clara County Sheriff's Office.
An employee on Torre Avenue never suspected a counterfeit operation was operating across the street.
"Nobody suspicious, or just looks out of the norm like they don't belong here," said Cupertino valet Oscar Portillo.