Unable to remove Signature from a digitally signed Excel 2007 spreadsheet

Problem

You’ve made an attempt to sign an Excel 2007 spreadsheet with a certificate but noticed that you receive the following warning note when you reopen the spreadsheet:

Signatures

This document contains invalid signatures.

You attempt to remove the signature clicking on the arrow pointing downwards then selecting Remove Signature:

… answer Yes to:

Are you sure you want to permanently remove this signature? This action cannot be undone.

… only to receive the following message:

Signatures cannot be added or removed because this read-only workbook has been changed. To add or remove signatures, enable editing, save your changes, and then try again.

You’ve verified that enabling macros does not change this behavior:

Solution

I usually don’t blog about Microsoft Office applications because I’m not at all savvy with Excel or the other applications in the suite but as I had to assist with signing various Excel documents today for a client and ran into this problem and only finding 3 posts via Google with no resolution, I thought it would be a good idea to blog the resolution.

After spending half an hour or so going through the Excel help files and navigating around the menus to find a button that switched to editing mode, the way I finally got around this error message to remove the signed certificate was to open the spreadsheet, click on the top left corner button then select Save As –> Excel Workbook:

Save the file with a new file name:

Continue selecting Yes to the following message:

Saving a copy of this workbook will invalidate all of the signatures in the copy. Do you want to continue?

With the new file created:

… proceed with opening the file:

Click on the View Signatures… button:

Click on the arrow pointing downwards under the Invalid signatures window and select Remove Signature:

… answer Yes to:

Are you sure you want to permanently remove this signature? This action cannot be undone.

… and because you saved the original Excel spreadsheet to a new file, the signature should now successfully remove:

The signature has been removed and the document has been saved.

You don’t need to save the document at this point so you can just close it.

As easy as the process seems, it took me a bit of time to figure this out.  Hope this helps anyone out there who may come across this