The following should do the trick when run as a script from a rule that acts on all messages (or all messages from a particular sender)
The code will adapt to either scenario, but if you are moving to a sub folder of Inbox called "Old Transactions" that folder must exist.
You can test the code on a selected message using the TestCode macro.
Option Explicit

Sub TestCode()
Dim olMsg As MailItem
    On Error Resume Next
    Select Case Outlook.Application.ActiveWindow.Class
        Case olInspector
            Set olMsg = ActiveInspector.currentItem
        Case olExplorer
            Set olMsg = Application.ActiveExplorer.Selection.Item(1)
    End Select
    OldData olMsg
lbl_Exit:
    Exit Sub
End Sub

Sub OldData(olItem As MailItem)
Dim olInsp As Outlook.Inspector
Dim wdDoc As Object
Dim oRng As Object
Dim dDate As Date, dRecDate As Date
Dim sDate As String, sRecDate As String
Dim oFldr As Folder
    If TypeName(olItem) = "MailItem" Then
        If InStr(1, olItem.Body, "Transaction Date: ") > 0 Then
            Set oFldr = Session.GetDefaultFolder(olFolderInbox).folders("Old Transactions")
            With olItem
                Set olInsp = .GetInspector
                Set wdDoc = olInsp.WordEditor
                Set oRng = wdDoc.Range
                With oRng.Find
                    Do While .Execute("Transaction Date: ")
                        oRng.collapse 0
                        oRng.End = oRng.End + 21
                        If IsDate(oRng.Text) = True Then
                            dDate = CDate(oRng.Text)
                            sDate = Format(dDate, "yyyymmddHHMM")
                            dRecDate = DateAdd("n", -15, olItem.ReceivedTime)
                            sRecDate = Format(dRecDate, "yyyymmddHHMM")
                            If Val(sDate) < Val(sRecDate) Then
                                '    olItem.Delete
                                olItem.Move oFldr
                            End If
                        End If
                        Exit Do
                    Loop
                End With
            End With
        End If
    End If
lbl_Exit:
    Set oRng = Nothing
    Set wdDoc = Nothing
    Set olInsp = Nothing
    Set olItem = Nothing
    Set oFldr = Nothing
    Exit Sub
End Sub