Sub InvoicesUpdate()
'
'Application Settings
Application.ScreenUpdating = False
Application.DisplayAlerts = False
Application.Calculation = xlCalculationManual

'Instantiate control variables
Dim allRows As Long, currentOffset As Long, invoiceActive As Boolean, mAllRows As Long
Dim iAllRows As Long, unusedRow As Long, row As Long, mWSExists As Boolean, newmAllRows As Long

'Instantiate invoice variables
Dim accountNum As String, custName As String, vinNum As String, caseNum As String, statusField As String
Dim invDate As String, makeField As String, feeDesc As String, amountField As String, invNum As String

'Instantiate Workbook variables
Dim mWB As Workbook 'master
Dim iWB As Workbook 'import

'Instantiate Worksheet variables
Dim mWS As Worksheet
Dim iWS As Worksheet

'Instantiate Range variables
Dim iData As Range

'Initialize variables
invoiceActive = False
row = 0

'Open import workbook
Workbooks.Open ("path:excel_invoices.csv")
Set iWB = ActiveWorkbook
Set iWS = iWB.Sheets("excel_invoices.csv")
iWS.Activate
Range("A1").Select
iAllRows = iWS.UsedRange.Rows.Count 'Count rows of import data

'Instantiate array, include extra column for client name
Dim invoices()
ReDim invoices(10, 0)

'Loop through rows.
Do

    'Check for the start of a client and store client name
    If ActiveCell.Value = "Account Number" Then

        clientName = ActiveCell.Offset(-1, 6).Value

    End If

    If ActiveCell.Offset(0, 3).Value <> Empty And ActiveCell.Value <> "Account Number" And ActiveCell.Offset(2, 0) = Empty Then

        invoiceActive = True

        'Populate account information.
        accountNum = ActiveCell.Offset(0, 0).Value
        vinNum = ActiveCell.Offset(0, 1).Value
        'leave out customer name for FDCPA reasons
        caseNum = ActiveCell.Offset(0, 3).Value
        statusField = ActiveCell.Offset(0, 4).Value
        invDate = ActiveCell.Offset(0, 5).Value
        makeField = ActiveCell.Offset(0, 6).Value

    End If

    If invoiceActive = True And ActiveCell.Value = Empty And ActiveCell.Offset(0, 6).Value = Empty And ActiveCell.Offset(0, 9).Value = Empty Then

        'Make sure something other than $0 was invoiced
        If ActiveCell.Offset(0, 8).Value <> 0 Then

            'Populate individual item values.
            feeDesc = ActiveCell.Offset(0, 7).Value
            amountField = ActiveCell.Offset(0, 8).Value
            invNum = ActiveCell.Offset(0, 10).Value

            'Transfer data to array
            invoices(0, row) = "=TODAY()"
            invoices(1, row) = accountNum
            invoices(2, row) = clientName
            invoices(3, row) = vinNum
            invoices(4, row) = caseNum
            invoices(5, row) = statusField
            invoices(6, row) = invDate
            invoices(7, row) = makeField
            invoices(8, row) = feeDesc
            invoices(9, row) = amountField
            invoices(10, row) = invNum

            'Increment row counter for array
            row = row + 1

            'Resize array for next entry
            ReDim Preserve invoices(10,row)

         End If

    End If

    'Find the end of an invoice
    If invoiceActive = True And ActiveCell.Offset(0, 9) <> Empty Then

        'Set the flag to outside of an invoice
        invoiceActive = False

    End If

    'Increment active cell to next cell down
    ActiveCell.Offset(1, 0).Activate

'Define end of the loop at the last used row
Loop Until ActiveCell.row = iAllRows

'Close import data file
iWB.Close

Dim invoices()
Redim invoices(10,0)

ReDim Preserve MyArray(10,20) '<-- Returns Error

MyArray = ReDimPreserve(MyArray,10,20)

'redim preserve both dimensions for a multidimension array *ONLY
Public Function ReDimPreserve(aArrayToPreserve,nNewFirstUBound,nNewLastUBound)
    ReDimPreserve = False
    'check if its in array first
    If IsArray(aArrayToPreserve) Then
        'create new array
        ReDim aPreservedArray(nNewFirstUBound,nNewLastUBound)
        'get old lBound/uBound
        nOldFirstUBound = uBound(aArrayToPreserve,1)
        nOldLastUBound = uBound(aArrayToPreserve,2)
        'loop through first
        For nFirst = lBound(aArrayToPreserve,1) to nNewFirstUBound
            For nLast = lBound(aArrayToPreserve,2) to nNewLastUBound
                'if its in range, then append to new array the same way
                If nOldFirstUBound >= nFirst And nOldLastUBound >= nLast Then
                    aPreservedArray(nFirst,nLast) = aArrayToPreserve(nFirst,nLast)
                End If
            Next
        Next
        'return the array redimmed
        If IsArray(aPreservedArray) Then ReDimPreserve = aPreservedArray
    End If
End Function

Option explicit
'redim preserve both dimensions for a multidimension array *ONLY
Public Function ReDimPreserve(aArrayToPreserve As Variant, nNewFirstUBound As Variant, nNewLastUBound As Variant) As Variant
    Dim nFirst As Long
    Dim nLast As Long
    Dim nOldFirstUBound As Long
    Dim nOldLastUBound As Long

    ReDimPreserve = False
    'check if its in array first
    If IsArray(aArrayToPreserve) Then
        'create new array
        ReDim aPreservedArray(nNewFirstUBound, nNewLastUBound)
        'get old lBound/uBound
        nOldFirstUBound = UBound(aArrayToPreserve, 1)
        nOldLastUBound = UBound(aArrayToPreserve, 2)
        'loop through first
        For nFirst = LBound(aArrayToPreserve, 1) To nNewFirstUBound
            For nLast = LBound(aArrayToPreserve, 2) To nNewLastUBound
                'if its in range, then append to new array the same way
                If nOldFirstUBound >= nFirst And nOldLastUBound >= nLast Then
                    aPreservedArray(nFirst, nLast) = aArrayToPreserve(nFirst, nLast)
                End If
            Next
        Next
        'return the array redimmed
        If IsArray(aPreservedArray) Then ReDimPreserve = aPreservedArray
    End If
End Function