E-file your return, after mailing them, may result in the IRS
rejecting the e-filed return due to someone already filing using that
name, social security number and birthday.
Additionally, if there
is a refund due, submitting two returns will slow down your receiving
your refund because a person will need to investigate why two returns
were received. That is why is never recommended that you file the same tax return twice (once you've mailed your taxes they are considered filed).
