If you have sensitive data you'd like to keep from prying eyes in a Microsoft Excel file, the easiest way to protect it is with Excel's built-in password tools.

Open the Excel file you want to protect with a password. Click on File -> Info. Now select Protect Workbook. Select Encrypt with Password from the list. Now enter the password. Confirm it once ...

Sending Excel files containing crucial financial and business data has risks. To add a layer of protection, you should learn to password protect an Excel file.