Copying the content of one cell into another worksheet of the same workbook

Right click on Invoice Tab --> View Code --> And paste the code given below into the opened code window.

How this code works?

On Invoice Sheet, once you input a value for any date in col. B to col. AS, the sum of values in that row will be automatically be placed in the corresponding cell in col. AT and the sum in col. AT will be transferred to the general Sheet in col. D (Sales) automatically.
So your Invoice sheet contains no formula, you just need to input the figures between col. B to AS and all will be done automatically.
Input the data for next date on Invoice sheet and you will come to know how the code works.

I have also corrected some of your formulas on general sheet to avoid errors.

Here is the used code...

Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Cells.Count > 1 Then Exit Sub
Dim Dws As Worksheet
Dim r As Long
Set Dws = Sheets("general")
If Not Intersect(Target, Range("B:AS")) Is Nothing And Target.Row > 1 And Target <> "" Then
    Range("AT" & Target.Row).Formula = Application.Sum(Range(Cells(Target.Row, "B"), Cells(Target.Row, "AS")))
    Range("AT" & Target.Row).Value = Range("AT" & Target.Row).Value
    Range("AT" & Target.Row).Style = "Currency"
    If Application.CountIf(Dws.Columns(1), Cells(Target.Row, "A")) > 0 Then
        r = Application.Match(Cells(Target.Row, "A"), Dws.Columns(1), 0)
        Dws.Cells(r, "D") = Cells(Target.Row, "AT")
        Dws.Cells(r, "D").Style = "Currency"
    End If
End If
End Sub

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for details refer to the attached workbook.
August-2015.xlsm