If
you need to make a change to a
tax return that has already been filed,
whether for this year or for a prior year you must file an Amended Return (1040-X)
You
have to use the software appropriate for
that year.
The online software for prior years is no longer available. You may purchase the desktop software here: https://turbotax.intuit.com/personal-taxes/past-years-products
Generally,
to claim a refund, you must file Form 1040-X within 3 years after the date you filed your original return
or within 2 years after the
date you paid the tax, whichever is
later.
When you get into the software, type "amend" in the search box at the top of your screen.
TurboTax will display a "Jump to Amend". Click on that and TurboTax will walk you through the process.
