I e-filed my return and it was approved, however, I received an additional W-2 from 2018, in the mail. Do I need to file an amendment to this years return or separately?
A W-2 dated 2018 would need to be entered on a 2018 tax return and not a 2019 tax return. If you filed a 2018 return that did not include the W-2, you would need to amend the 2018 return.
See this article for assistance: https://ttlc.intuit.com/community/amending/help/how-to-amend-change-or-correct-a-return-you-already-...
To file a return for a prior tax year
If you need to prepare a return for 2016, 2017, or 2018 you can purchase and download desktop software to do it, then print, sign, and mail the return(s)
Remember to prepare your state return as well—if you live in a state that has a state income tax.
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
Note: The desktop software you need to prepare the prior year return must be installed/downloaded to a full PC or Mac. It cannot be used on a mobile device.
If you are getting a refund, there is not a penalty for filing past the deadline. If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.