Jul 12 2022 11:45 PM
@Priyanshu1325 It's not an error. Excel merely alerts you to the fact that you perhaps missed some cells in the formula. The header row shows "Jan-2019" but probably is a real date, hence a number. The formula sums B4 to B8 and Excel's background error checking thinks that you perhaps also want to include the number from B3. Obviously not, so you can ignore the alert.
Jul 13 2022 01:15 AM
If you find these warnings (not "errors") more annoying than helpful, you can disable so-called "background error checking" altogether, or you can pick-and-choose which warnings you want.
Navigation to the option might vary with the Excel version. In Excel 2010, I click File > Options > Formulas to find the following options.
Click next to "Enable background error checking" to remove the checkmark.
Click "Reset Ignored Errors" to remove pre-existing warnings in cells.