I'm filing for my mom who passed in 2023. Where do I indicate this on the tax return?

In the Personal Info section of the return after entering the taxpayer's name, Social Security number, and other basic information, there is an additional screen asking if any special situations apply.  One of those check boxes states that the taxpayer passed away before filing the return.  When it is checked, you will be asked to enter the date of death.

My condolences for your loss.

Personal Info, enter first few answers (name, birth date, etc.)

Do Any of These Apply: check the Passed away before filing" box