Kenneth John Olsen was arrested at about 9:45 p.m. Friday at 3091 Red Maple Court, police said.
The Vacaville Police Department began an investigation in May when they were told by United Postal Service officials that Olsen was mailing hundreds of envelopes to various parts of the country and was using fraudulent billing codes, according to police.
Investigators later found that those envelopes contained fraudulent checks believed to be created by Olsen, police said.
During a search of Olsen's home, investigators found check making software, UPS and FedEx shipping materials and international correspondence, as well as numerous printed but unmailed checks, according to police.
The checks were being prepared for mailing and totaled more than $500,000. Other evidence in the home suggested that Olsen had been creating the fraudulent checks for several months, police said.
Anyone with information about the investigation is asked to contact Vacaville police Officer Chris Lechuga at (707) 449-5200.