Pardon the lack of detail in my initial post- still a fairly green staff accountant. Much to learn 🙂

The other partner in this S-corp is the deceased's trust.

The S-corp now has a single shareholder, different than the deceased and their trust listed for 2020. This new shareholder, who has 100% now (obviously), was the Managing Director without any stock prior to 2021. 

That also being said, I'm not entirely sure how to determine if the books were cut off as of the date of death, or if the income/loss was allocated on a per share per day basis. What I do see is that at the beginning of the year in 2020, 100% of the shares were in the deceased's name, and by the end of the year, 100% of the shares are allocated to the trust. 

The 2020 return that I am assisting to amend was prepared by another CPA firm and I have very little information on this return.