Common Issues and Workarounds with Excel File Formats

This page contains information on common issues with Excel file formats, as well as workarounds to help address them.


Excel Extension Mismatch Warning

A warning of an extension mismatch may appear when exporting a file to Excel, as displayed in the figure below:


format and extension mismatch warning

Possible “File Format and Extension don’t Match” error causes

Incorrect extension – in most cases, this issue occurs because the Excel file is of a different format than its extension shows. This may happen automatically after the file is converted, or manually, after a user intervention. In such a case, the issue can be fixed by changing the extension manually to a correct one.

Excel file is blocked – if the Excel file was obtained from an e-mail attachment, it may be set to Blocked in the file’s properties. Many e-mail providers block such files automatically for security purposes. In such a case, unblock the file in its properties.

The file is incompatible with Excel – This issue may occur due to its incompatibility with Excel. To resolve this issue, try to open the file with other spreadsheet software, such as OpenOffice Calc.

Protected Views is enabled – A security option may prevent Excel from opening certain files, such as those that are received as email attachments. To resolve this issue, open Excel settings and disable Protected Views from the Trust Center menu.

The message is not disabled – To avoid updating your Office to the latest version in which this issue is resolved, it is possible to circumvent the error by disabling the warning message. In such a case, use the Registry Editor to create an ExtensionHardening value.


Method 1: Changing the extension manually

  1. Open File Explorer and select the View tab. On the ribbon, ensure that File Name Extensions is enabled

    file name extensions option
  2. Right-click on the file, and select Rename

  3. Modify the file extension to .xls, .xlsx or .xlsm, attempting to open the file after each extension change

  4. One of these extensions should open the file without triggering the error message

Method 2: Unblocking the file

  1. Right-click on the file and select Properties

  2. In the General tab, go to the Security section and check Unblock

  3. Select Apply and then OK, and open the file to ensure the error no longer appears

Method 3: Disabling Protected View

Note: The following steps should work for 2010 or later versions of Excel.

  1. Open Excel and select File from the ribbon. In the File menu, select Options on the left-hand side pane

  2. Select the Trust Center tab and select Trust Center Settings

  3. Select Protected Views, and uncheck all the boxes associated with Protected View

  4. Select OK and open the file.

Method 4: Disabling the warning message

  1. Press the Windows key + R to open the Run command, enter regedit and select OK

  2. When prompted by UAC (User Account Control), select Yes to grant administrative privileges and open the Registry Editor

  3. Navigate to the following location: HKEY_CURRENT_USER\Software\Microsoft\Office\*X*\Excel\Security

  4. Right-click in an empty space in the right-hand pane and select New and then DWORD (32-bit) Value. Name the value ExtensionHardening.

  5. Double-click on the value and set Base to Hexadecimal and the value to 0

  6. Close the Registry Editor and restart the system

  7. Open the file to confirm that the error message no longer appears


CSV File Separator

BSS users can export Product, Account and other object tables from BSS as CSV files. It is possible that when they try to open the CSV file using Excel, the file is not displayed as expected, e.g. the data are not displayed under the correct columns. This happens because Excel does not recognize the delimiter used in the CSV files exported from BSS, which is the semicolon (;).

A proposed workaround, which will allow users to directly open the CSV files using Excel is the following (Windows 10):

  1. Open the Start menu and select Settings

  2. Select Time & Language

  3. Select Region, and then select Additional date, time & regional settings

  4. Select Change date, time or number formats

  5. On the Format tab, select Additional Settings

  6. In Number tab, change List separator to ;

  7. Select Apply and then OK

  8. The changes will take effect after restarting the PC.