FIFO Based Receipt Adjustment To determine date when particular invoice is finally cleared

Hi

check this attachment..maintain data as per two sheet & click on blue button to run code:

updated code is:

Sub fifoadjustment()
Dim i As Integer, j As Integer, customer As String
Dim payment_bal As Long, invoice_bal As Long, invoice_amt As Long
Dim assigned As Long

payment_bal = 0
invoice_bal = 0
invoice_amt = 0

Sheets("Payments").Range("E2:E50000").Value = ""
Sheets("Invoice").Range("E2:E50000").Value = ""

For i = 2 To Sheets("Invoice").Range("A55000").End(xlUp).Row
invoice_amt = Sheets("Invoice").Cells(i, 2).Value
customer = Sheets("Invoice").Cells(i, 3).Value
invoice_bal = 0
payment_bal = 0
assigned = 0
    For j = 2 To Sheets("Payments").Range("A55000").End(xlUp).Row
    If Sheets("Payments").Cells(j, 3).Value = customer Then
    If Sheets("Payments").Cells(j, 5).Value = "" Then
            If invoice_bal = 0 Then
               If Sheets("Payments").Cells(j, 2).Value < invoice_amt Then
                  invoice_bal = invoice_amt - Sheets("Payments").Cells(j, 2).Value
                  payment_bal = 0: Sheets("Payments").Cells(j, 5).Value = 0
                  
               End If
            Else
                  assigned = Application.WorksheetFunction.Min(Sheets("Payments").Cells(j, 2).Value, invoice_bal)
                  invoice_bal = invoice_bal - assigned 'Application.WorksheetFunction.Min(Sheets("Payments").Cells(j, 2).Value, invoice_bal)
            End If
            If invoice_bal = 0 Then
               Sheets("Invoice").Cells(i, 5).Value = Sheets("Payments").Cells(j, 1).Value
               If assigned = 0 Then
               payment_bal = Sheets("Payments").Cells(j, 2).Value - invoice_amt
               Else
               payment_bal = Sheets("Payments").Cells(j, 2).Value - assigned
               End If
               Sheets("Payments").Cells(j, 5).Value = payment_bal 'Sheets("Payments").Cells(j, 5).Value - assigned
            Else
               Sheets("Invoice").Cells(i, 5).Value = "Amt recieved " & invoice_amt - invoice_bal
            End If
    
    Else
        If Sheets("Payments").Cells(j, 5).Value <> 0 Then
            If invoice_bal = 0 Then
               If Sheets("Payments").Cells(j, 5).Value < invoice_amt Then
                  invoice_bal = invoice_amt - Sheets("Payments").Cells(j, 5).Value
                  payment_bal = 0: Sheets("Payments").Cells(j, 5).Value = 0
               End If
            Else
                  assigned = Application.WorksheetFunction.Min(Sheets("Payments").Cells(j, 5).Value, invoice_bal)
                  invoice_bal = invoice_bal - Application.WorksheetFunction.Min(Sheets("Payments").Cells(j, 2).Value, invoice_bal)
            End If
            If invoice_bal = 0 Then
               Sheets("Invoice").Cells(i, 5).Value = Sheets("Payments").Cells(j, 1).Value
               If assigned = 0 Then
               payment_bal = Sheets("Payments").Cells(j, 2).Value - invoice_amt
               Else
               payment_bal = Sheets("Payments").Cells(j, 2).Value - assigned
               End If
               Sheets("Payments").Cells(j, 5).Value = payment_bal 'Sheets("Payments").Cells(j, 5).Value - assigned
            Else
               Sheets("Invoice").Cells(i, 5).Value = "Amt recieved " & invoice_amt - invoice_bal
            End If
        End If
    End If
    End If
    Next j
Next i
End Sub

Cheers!!