The IRS allows electronic filing of tax returns for the current tax year only. Prior year returns can only be filed electronically by registered tax preparers, and only when the Modernized e-File System is available. The IRS posts the status of the Modernized e-File (MeF) system on the IRS Modernized e-File (MeF) Status webpage.
Individuals filing their own prior year return must print/mail the return.
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.