Sorry for your loss,
You are able to find this information in the Spousal Personal Information tab
Steps to enter spouses birthday:
Thank you for choosing TurboTax
im using turbotax 20, need to enter deceased spouse DOB, keeps coming up as error but no place to enter
@IMAXITED I will let our development team know about this omission. Thank you for pointing it out. In the meantime, you can enter the DOB using Forms mode. To do this, click the Forms icon on the blue menu bar. Click the Forms icon again and search for “info”. Select “INFOWS” from the list, then click the “OK” button. You can enter the spouse’s information on page 2 of 3.
To get back to EasyStep mode, just click the EasyStep icon on the blue menu bar.