When you are entering the taxpayers information there will be a screen labeled Let's check for some other situations. Check the box I am preparing this return for (name of taxpayer), who has passed away.
When filing the final tax return for a deceased person, TurboTax Online will ask whether the return is being filed for someone who has passed away in the My Info section. TurboTax will then report "Deceased" on the return. On the page titled Let's check for some other situations, put a check mark next to I am preparing this return for [Name], who has passed away, and enter the date of death.
The filing of a deceased taxpayer's final return usually falls to the executor or administrator of the estate, but if neither is named, then the task needs to be taken over by a survivor of the deceased, i.e. yourself.
The final return is filed on the same form that would have been used if the taxpayer were still alive, but "deceased" is written after the taxpayer's name. The deadline to file a final return is the tax filing deadline of the year following the taxpayer's death.
Only income earned between the beginning of the year and the date of death should be reported on the decedents’ final return. Earnings after the date of death are taxable to the beneficiary of the account or to the estate.
For more information, please read this TurboTax article.