Entering POET info while creating invoice for a 2 way non project PO

Hello All,

I am creating a 2 way PO with destination_type as Expense. At this point, i am not providing any project related information. Now while creating invoice for this PO, i want to enter POET fields at invoice distribution level. But these fields are greyed out. Can anyone please suggest me why these fields are greyed out and how can i achieve this?

Thanks In Advance.