Yes, you can amend a 2017 tax return. Amended returns must be mailed. If you filed your original return with TurboTax see the following on how to amend a return.
How do I amend a 2017 return in TurboTax?
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If you did not file your 2017 return with TurboTax, you would need to purchase the 2017 Desktop software, enter all your original information into the return, trick the software into thinking you filed by choosing to file by mail, then you can amend your return.
