You can not add the form/information to your original tax return once it has been filed AND accepted by the IRS. If it gets rejected, however, just log back in to your tax return add the form and make any other necessary corrections.
If accepted, you will need to file an amended return (1040X)
to show the additional form/information. You should not try to amend your
return until the original return has been fully processed and you have received
your refund or your payment has cleared.
Amended returns do not “catch up” to your original return
and replace them; they are processed as two separate returns.
Amended returns have to be printed and filed by mail. It can take the IRS up to 12 weeks or longer
to process them. If you are due a
larger refund than on your original return, your amended return should only
show the difference and you will receive a separate check for it. If you owe money on your amended return, it
will show only the new amount owed, you will have to mail a check with the
Click here for the 1040X: https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed
Please read this TurboTax FAQ for more information about qualifications for the Earned Income Credit (EIC or EITC): https://ttlc.intuit.com/replies/3299933