I have a 1099-B form from Etrade of stock I sold in 2017. Apparently forgot to file it last year. How do I handle it ?

[JohnW15 · Accepted solution]

You'd need to report this transaction on your 2017 return; you can't claim 2017 income transactions on your 2018 return.  If you've already filed your 2017 return, you'd need to amend that return with Form 1040-X.

Please see the TurboTax FAQ "How do I amend a 2017 return in TurboTax?" for additional information.

https://ttlc.intuit.com/replies/6603004

Please bear in mind that an amended return must be printed, signed and mailed to the IRS.  It cannot be eFiled.