Helping my dad w his taxes (usually for my parents but mom passed away) - he cashed out her IRA, does he have to pay tax or can it be excluded as an inheritance?

They both were 75+ in 2023. My dad received a 1099-R with Distribution code of 7 under box 7 and Total Distribution checked. I tried to choose inherited in the Turbo Tax desktop software but it didnt reduce the amount of tax owed.