The 42-year-old, believed to be an accountant, was taken to the Dungannon police station for questioning on Thursday [August 20] as part of an investigation into fraud and money laundering.
Searches were carried out at business premises in Belfast, Tyrone and Fermanagh but the suspect was arrested in County Tyrone.
Detective Chief Inspector Ian Wilson said: “We have launched an investigation following a number of complaints from farmers about the management of their business affairs.
“We are liaising with the Chartered Accountants Regulatory Board and HM Revenue and Customs.
“The investigation is at an early stage: a substantial amount of documents will need to be examined and our enquiries will continue for some time.”