Help! Message: The file format and extension of .xls don't match.

Copper Contributor

I have a many-years-old excel file that just this morning gave me the message "The file format and extension of 'Ameriprise Monthly.xls' don't match".


I am a non-tech user. That "Ameriprise Monthly" is the name of my file. I opened and looked at it just yesterday and it was fine. I have other .xls files that are fine. Basically I can open and close these files - that is my knowledge.


Is there somewhere I can upload this file so that a Microsoft expert can look at it and fix it? I don't see an option to attach a file here.


4 Replies
I'm having a similar problem. Have you already solved this problem? If you have, could you please do me a favor? Thanks very much in advance:)

@April_han No solutions to date. Looks like I just rebuild the file. ( Although I’ve made a second back up copy of every other important Excel file I have. Better late than never.)


The only thing I can offer you is some general advice on how to fix this problem.

Here are a few steps you can try:

  1. Add-ins: Disable any Excel add-ins you have installed, especially those that might be interacting with Excel files or the file system. You can usually find these in Excel under the "File" menu, select "Options," and then go to the "Add-ins" section.
  2.  Antivirus Software: Your antivirus software might be configured to scan files as they are opened or accessed. Temporarily disable your antivirus software and try opening the file again. If the file opens without issues, you may need to adjust the settings of your antivirus software to exclude Excel files or the specific folder containing your files.
  3. File Permission: Ensure that you have the necessary permissions to access and modify the file. Right-click on the file, choose "Properties," and check the security and permissions settings.
  4. Network Drives: If the file is stored on a network drive, there could be issues with network connectivity, permissions, or drive mapping. Try copying the file to your local machine and opening it from there.
  5. File Compatibility: Ensure that the file you are trying to open is indeed in the older Excel (.xls) format. Sometimes, file extensions can be changed or the file format might have been inadvertently modified.
  6. Open with Compatibility Mode: If you are using a newer version of Excel (e.g., Excel 2016 or later), try opening the file using the "Compatibility Mode." Open Excel, go to File > Open, select your file, and choose "Open with Compatibility Mode" if available.
  7. File Repair: Use Excel's built-in repair functionality. Open Excel, go to File > Open, select your file, and choose "Open and Repair" from the dropdown menu.
  8. Save As New File: Open the file, go to File > Save As, and save it with a new name. This can sometimes resolve issues with file corruption.
  9. Online File Repair Services: There are online services that claim to repair corrupted Excel files. However, use such services cautiously, and ensure they are from reputable sources. Always make a backup of your file before using such services.

Remember to always keep backups of important files to prevent data loss. If you have access to another computer or a Windows machine, you could also try opening the file there to see if the issue persists. Again, please be cautious about sharing sensitive information or files online, and make sure to follow best practices for file security.

NOTE: before you carry out the above steps, be sure to UPDATE in advance!

My knowledge of Excel on mac is limited, but since no one has answered it for at least one day or more, I entered your question in various AI. The text and the steps are the result of various AI's put together. Maybe it will help you, if not please just ignore it.


My answers are voluntary and without guarantee!


Hope this will help you.

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This will help all forum participants.

Thanks for the effort - I very much appreciate it.