copy cells from sheets based on date, paste to another sheet

Then you need to assign a variable to stand for that cell you are trying to copy. Its hard to tell where because your code is too spaced out but:
I think right here you'd go

If ActiveCell.Value + Month(ActiveCell.Offset(0, 1).Value) < Today Then ' if contract start plus one frequency period is before present date
    CellAddress = ActiveCell.Address
    Call enterdata                   ' create entries on Receipts & Payments

You need to dim CellAddress as a String.

Then when you get to the line that was causing you trouble, you should be able to go

ActiveCell.Value = Sheets("CoA").Range(CellAddress).Value