While there is no minimum age to file a tax return, there is one to efile it:
Per the IRS Modernized E-File Manual:
The following taxpayers are ineligible to sign individual income tax returns with an electronic signature using the Self-Select PIN:
• Primary taxpayers under age sixteen who have never filed; and
• Secondary taxpayers under age sixteen who did not file the prior tax year.
Age is determined as of Dec 31 of the tax year (so, 12/31/2018).
