Copy and Paste Row If Condition is Met

Should the bold word not be "PaySide" instead of "SendSide" ?

If Worksheet.FillOutThisForm.Range("E:E") contains the word "Payee", find the row in Worksheet.Payside1 that contains the corresponding unique identifier in column L of Worksheet.FillOutThisForm. Then, copy and paste the entire row from Worksheet.SendSide and paste in the next available row in Worksheet.Subjects.

Assuming its a typo at your end, use this code where Sender uses Sendside and Payee uses Payside sheets -

Option Explicit

Sub copy_data()
Dim i As Long, lrow As Long, lrow1 As Long, lrow2 As Long
Dim rngcopy As Range

Application.ScreenUpdating = False

With Worksheets("Fill Out This Form")
    lrow = .Range("E" & .Rows.Count).End(xlUp).Row
    lrow1 = Worksheets("Sendside").Range("A" & Rows.Count).End(xlUp).Row
    lrow2 = Worksheets("Payside").Range("A" & Rows.Count).End(xlUp).Row
    For i = 3 To lrow
        If .Range("E" & i).Value = "Sender" Then
            Worksheets("SendSide").Range("A1:H" & lrow1).AutoFilter field:=1, Criteria1:=.Range("L" & i).Value
            Set rngcopy = Worksheets("SendSide").Range("A2:H" & lrow1).SpecialCells(xlCellTypeVisible)
            rngcopy.Copy Worksheets("Subjects").Range("A" & Rows.Count).End(xlUp).Offset(1, 0)
            Set rngcopy = Nothing
        ElseIf .Range("E" & i).Value = "Payee" Then
            Worksheets("PaySide").Range("A1:H" & lrow2).AutoFilter field:=1, Criteria1:=.Range("L" & i).Value
            Set rngcopy = Worksheets("PaySide").Range("A2:H" & lrow2).SpecialCells(xlCellTypeVisible)
            rngcopy.Copy Worksheets("Subjects").Range("A" & Rows.Count).End(xlUp).Offset(1, 0)
            Set rngcopy = Nothing
        End If
    Next i
End With

Worksheets("SendSide").Rows(1).AutoFilter
Worksheets("PaySide").Rows(1).AutoFilter

MsgBox "Done"

Application.ScreenUpdating = True

End Sub

Copy the Excel VBA code
Select the workbook in which you want to store the Excel VBA code
Hold the Alt key, and press the F11 key, to open the Visual Basic Editor
Choose Insert | Module
Where the cursor is flashing, choose Edit | Paste

To run the Excel VBA code:
Choose View | Macros
Select a macro in the list, and click the Run button

Oops i forgot to mention that you need to have headers in the SendSide and PaySide files for it to work properly.

How did you adjust it?