If you've e-filed your return and Form 8862 was required, the IRS will most likely reject your return, and you can then submit Form 8862 when you re-transmit your return.
Please see the TurboTax Help article “E-file reject F1040-164-01: Form 8862 is missing from the tax return and it is required to be able to claim the earned income credit (EIC)” for guidance.
If you paper-filed your return and Form 8862 was required, you'll need to wait for the IRS to contact you to send in the form. Filing another return with Form 8862 attached, before the IRS contacts you, could cause serious delay in receiving your refund.
How do I submit 8862 after my federal, and state were rejected
I DIDNT FILE ELECTRONICALLY THROUGH THE GOVERNMENT’S WEBSITE! I filed through Intuit and it did not file or offer me the federal EIC credit which I am eligible for it. What do I do?!
If you need to enter your 8862, here is how you enter Form 8862.