Yes, you can amend your 2019 tax return to include your dependent. It will change the entire return calculation and most likely your eligibility for the Premium Credits, and your tax bill won't be that big.
If you used TurboTax Online, simply log in to your account and select “Amend a return that was filed and accepted.” If you used our CD/download product, sign back into your return and select “Amend a filed return.” You must file a separate Form 1040X for each tax return you are amending.
