It is in your best interest to file your late returns. The IRS will not consider an Offer in Compromise or Installment Agreement unless you have filed all outstanding returns. In most cases the IRS will not prosecute late filers beyond penalties and interest. Only in rare cases will a late filer be prosecuted. When filing a late return, the taxpayer should go back six years unless the IRS has filed a substitute return. If this is the case, then it is likely that if you had filed the return yourself the taxes would have been far less. It will benefit you to file for those years to decrease your taxes owed. When filing a late return, it is to your advantage to have a professional to help you with both the filing of the return and in dealing with the IRS.