My Dad passed in 2019. We filed a joint return for my Mom and Dad for 2019. Mom received a 2020 1099-INT form from the IRS with my Dad's Identification # on, how do I handle this? Can I report this on Mom's federal tax return for 2020?
If the IRS paid interest to both your parents (perhaps because they filed a joint return, and their refund was paid late so the IRS added interest), then the income is really to both your parents even though the IRS only listed your father's SSN. In that case, I would say it is acceptable to include it on your mother's tax return.
Yes, you would just enter it on your mother's return since she was the only one alive in 2020.
She needs to get your father's name and ssn removed from the account as soon as possible so it will be reported in her ssn.
Since your father's ssn was first on the account, she may get a letter of inquiry from IRS about it.
Their 2019 joint return should have reported your father as deceased so IRS won't continue to expect returns from your father.
Incidentally, your mother needs to start a new account in Turbotax with a clean slate. The fact that the interest was issued with your father's name means that he was listed as the "first" taxpayer on the joint return. Using Turbotax online, it is almost impossible to remove his information from all the hidden areas of the program, even if she tries to change her status to "single" and file in her name. Therefore, she needs to create a clean account just for herself now.