Hello I have a question. What happens if you already filed your taxes but did not file your 8962 with the 1095-a because you did not know it existed?? When can I amend?

[DoninGA]

If you entered the Form 1095-A on the 2019 tax return, the Form 8962, Premium Tax Credit is automatically generated and included with your tax return.

[LeonardS]

If you have filed your tax return and then discover that you have Form 8962 to file you will have to wait until the IRS either accepts or rejects your tax return.

If the return is rejected you will correct the error that caused the rejection, add Form 8962 and refile your return.

If the return was accepted by the IRS then you will have to file an amended tax return using Form 1040X to add Form 8962 to your tax return

. 

This link to the TurboTax Help page  How to amend (change or correct) a return you already filed provides information on how to amend your tax return.