Once a non-filer has been identified, a series of computer-generated notices are mailed to the taxpayer at their last known address. Where no response is received on the notices the case is assigned to the Collection Division of the IRS. The Automated Collection System (ACS) within the Collection Division may eventually attempt to contact a taxpayer by telephone seeking the delinquent returns. If ACS is unable to secure the delinquent returns, a Revenue Officer may be assigned to contact the taxpayer in person at their home or place of business. The Revenue Officer has the option of determining if fraud has been committed by the taxpayer, in which case a referral may be made to CID for possible prosecution.