VBA Issues surronding Check Boxes on To Do List

When checking a box (column B) I would like the date the box was checked to appear in the date completed column (Column J)

You just had wrong column assigned.

Sub Process_CheckBox()

   Dim cBox As CheckBox
   Dim LRow As Integer
   Dim LRange As String
   
   LName = Application.Caller
   Set cBox = ActiveSheet.CheckBoxes(LName)
   
   'Find row that checkbox resides in
   LRow = cBox.TopLeftCell.Row
   LRange = "J" & CStr(LRow)
   
   'Change date in column B, if checkbox is checked
   If cBox.Value > 0 Then
      ActiveSheet.Range(LRange).Value = Date
      
   'Clear date in column B, if checkbox is unchecked
   Else
      ActiveSheet.Range(LRange).Value = Null
   End If
   
End Sub

The ability to move checked rows to another tab

Just the data, correct?

A formula to accurately calculate the "Percent Complete"

Working on this one.

You probably don't have the right macro assigned to the checkbox. Right click the checkbox and select Process_CheckBox.

Here's the code for calculating the open tasks.

Add UpdateChart to the bottom of Process_CheckBox.

Sub UpdateChart()
Dim WS As Worksheet
Dim A As Long
Dim LastRow As Long
Dim Shp As Shape
Dim Ctr As Long

Set WS = Worksheets("Tasks")

With WS
    LastRow = .Cells(.Rows.Count, "C").End(xlUp).Row
    
For Each Shp In WS.Shapes
    If InStr(Shp.Name, "Check Box") > 0 Then
        If Shp.ControlFormat.Value = xlOn Then
            Ctr = Ctr + 1
        End If
    End If
Next
End With

With WS.ChartObjects("Chart 2").Chart
    WS.Range("P5") = Ctr / LastRow
End With
End Sub

OK, there is the completed version.

There are some problems with your checkboxes. There are five places where there are two checkboxes on top of each other. It was preventing the checkbox from clearing. If you can use this workbook, it will be easier than trying to find those again. (It was row 64, 65, 94, and I can't remember the other two)

All code is in Module 1.