• Microsoft can’t retrieve forgotten passwords.          

  • There are no restrictions on the passwords you use with regards to length, characters or numbers, but passwords are case-sensitive.

  • It’s not always secure to distribute password-protected files that contain sensitive information.

  • Be cautious when sharing files or passwords with other users. You still run the risk of passwords them falling into the hands of unintended users. Remember that locking a file with a password does not necessarily protect your file from malicious intent.

Follow these steps to encrypt an Excel file:

Click File > Info > Protect Workbook > Encrypt with Password

When you/another user tries to open the file, the following screen appears: