Thanks, @Mike9241. It was included in Accounts Receivable.
She already amended that return once (this wasn't the only error), plus I would have to amend my personal as well, so I hope to find another solution even if it's not perfect.
I see that schedule M-2 part b on 1120S specifically lists "Shareholders Undistributed Income Previously Taxed", which seems to be a good fit. Or is this referring to something else?
