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

Ok, I see what the problem is. Give me a bit to fix it, I'm pretty busy with my real job today.

Ok, I rewrote your code. Here are a couple of issues:
1) You don't need to select things. Look closely at how I reworked all the "Select" code to make it more efficient. It will run much faster this way.
2) Your Frequency select between months cells don't work. The Month() function tells you what month the date you put in is in. For example, Month(Date) = 10 (October is the tenth month). Dates are stored as integers in excel. Since you put 1 and 3 in those cells, you are actually looking at 1/1/1900 and 1/3/1900. If you want to add a month, put 30 in those cells and just add the cell value instead of using the month code.
3) The reason it was giving you this last error was the scope of the variable was local. To make it work, above both modules define it as public. For example: Public yourvariable as String.

Go through this code and see the changes carefully. I put the revised code near the commented out lines of your code so you could see how they correspond. Then after, go ahead and delete out your code. If it is then not working properly, let me know and we'll tweak some more.

Sub CheckPaySchSO()
'
' Macro recorded 20/10/2009 by Philip Sharp
Dim intLSORow As Integer 'Last cell in Standing Orders table
Dim CellAddress As String
Dim Today As Date
Dim a As Integer

Today = Date
intLSORow = Sheets("CoA").Cells(47, "I").End(xlDown).Row
    
Sheets("CoA").Activate

'Do While ActiveCell.Value <> ""
For a = 47 To intLSORow
    If Sheets("CoA").Cells(a, "I").Value < Today Then
    'If ActiveCell.Value < Today Then ' checks to see if contract date is before the present date - if yes go to next evaluation
        If Sheets("CoA").Cells(a, "P").Value = "" Then
        'If ActiveCell.Offset(0, 7).Value = "" Then ' if there is no previous accounting entry date then
            If Cells(a, "I").Value + Sheets("CoA").Cells(a, "J").Value < Today Then
            'If ActiveCell.Value + Month(ActiveCell.Offset(0, 1).Value) < Today Then ' if contract start plus one frequency period is before present date
                 'CellAddress = Sheets("CoA").Cells(a, "I").Address
                 Call enterdata(a)                   ' create entries on Receipts & Payments
            End If
        Else
            'If ActiveCell.Offset(0, 7).Value + Month(ActiveCell.Offset(0, 1).Value) < Today Then    ' if last entry plus one frequency period is before present date
            If Sheets("CoA").Cells(a, "P").Value + Sheets("CoA").Cells(a, "J").Value < Today Then
                 'CellAddress = ActiveCell.Address
                 Call enterdata(a)                   ' create entries on Receipts & Payments
            End If
        End If
    End If
Next a

End Sub

Private Sub enterdata(intRowNum As Integer)

Dim CellAddress As String
Dim Today As Date
Dim intNRPRow As Integer 'Next row in Receipts and Payments Table.

Today = Date
intNRPRow = Sheets("Receipts & Payments").Cells(10, "A").End(xlDown).Row + 1

With Sheets("Receipts & Payments")
    .Cells(intNRPRow, 1).Value = Sheets("CoA").Cells(intRowNum, "I").Value
    .Cells(intNRPRow, 2).Value = Sheets("CoA").Cells(intRowNum, "K").Value
    .Cells(intNRPRow, 3).Value = Sheets("CoA").Cells(intRowNum, "L").Value
    .Cells(intNRPRow, 4).Value = Sheets("CoA").Cells(intRowNum, "N").Value
    .Cells(intNRPRow, 5).Value = Sheets("CoA").Cells(intRowNum, "M").Value
    .Cells(intNRPRow, 11).Value = Sheets("CoA").Cells(intRowNum, "O").Value
End With


'ActiveWorkbook.Sheets("Receipts & Payments").Activate
'Range("a10").Select
'
'    Do
'    If IsEmpty(ActiveCell) = False Then
'    ActiveCell.Offset(1, 0).Select
'    End If
'
'    Loop Until IsEmpty(ActiveCell) = True
'
'    ActiveCell.Value = Sheets("CoA").Range(CellAddress).Value
'    ActiveCell.Offset(0, 1) = Sheets("CoA").Range(CellAddress).Offset(0, 2).Value
'    ActiveCell.Offset(0, 2) = Sheets("CoA").Range(CellAddress).Offset(0, 3).Value
'    ActiveCell.Offset(0, 3) = Sheets("CoA").Range(CellAddress)(0, 5).Value
'    ActiveCell.Offset(0, 4) = Sheets("CoA").Range(CellAddress).Offset(0, 4).Value
'    ActiveCell.Offset(0, 10) = Sheets("CoA").Range(CellAddress).Offset(0, 6).Value
'
'    ActiveWorkbook.Sheets("CoA").Activate
'    Range("I47").Select
 
'If ActiveCell.Value + Month(ActiveCell.Offset(0, 1).Value) < Today Then
If Sheets("CoA").Cells(intRowNum, "I").Value + Sheets("CoA").Cells(intRowNum, "J").Value < Today Then
        'ActiveCell.Offset(0, 7).Value = ActiveCell.Value + Month(ActiveCell.Offset(0, 1).Value)
         Sheets("CoA").Cells(intRowNum, "P").Value = Sheets("CoA").Cells(intRowNum, "I").Value + Sheets("CoA").Cells(intRowNum, "J").Value
        ' if contract start plus one frequency period is before present date
'Else: ActiveCell.Offset(0, 7).Value = ActiveCell.Offset(0, 7).Value + Month(ActiveCell.Offset(0, 1).Value)
Else: Sheets("CoA").Cells(intRowNum, "P").Value = Sheets("CoA").Cells(intRowNum, "P") + Sheets("CoA").Cells(intRowNum, "J").Value
                            
End If
                
End Sub