If you keep it in your tax return...it keeps all the employer information so you do not have to retype it....but all the $$ boxes are now empty, waiting for you to manually enter the data from your paper form.
IF you know that you can import it this year,,,,then you can go ahead and delete it ...but YOU have to initiate the W-2 file import from the W-2 provider on the Wages&Income page.
A lot of people cannot get their W-2 as a imported file, so they like to have the old form available to use without having to type in all the information again. So they would not delete the empty W-2 since they are going to use it again.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
