Sometimes even when your return is accepted, the IRS may need more information to complete your return. If you purchased health insurance in 2016 through Healthcare.gov or your state’s Health Insurance Marketplace, you may qualify for a tax credit based on your income. Form 8962, Premium Tax Credit, is used to determine the amount of your Premium Tax Credit.
If your return has already been efiled and accepted and it was sent in without this information, the IRS is looking for this in order to finish processing your return. You can go through the steps to amending your return in order to generate the form after the fact.
HOW TO AMEND YOUR RETURN
HOW TO ENTER HEALTHCARE INFORMATION (FORM 1095-A)