Electronic filing.   Electronic filing is required for each return reporting 25 or more transactions a month. However, all taxpayers are encouraged to file electronically. File Form 720-TO and 720-CS electronically through the Excise Summary Terminal Activity Reporting System (ExSTARS). For more information on e-file and ExSTARS, visit the IRS website at www.irs.gov/excise. Also, see Pub. 3536, Motor Fuel Excise Tax EDI Guide.