Error: "The file format and extension of '<filename>' don't match. The file could be corrupted or unsafe"

In MYOB Accountants Enterprise (AE) when exporting the Tax homepage to Excel 2013 or 2016, opening the spreadsheet yields the warning "The file format and extension of '<filename>' don't match. The file could be corrupted or unsafe."

This is merely a warning and can be accepted so as to view the document's contents.

To avoid this message:

Save the document as a different file type.