In the example shown, the UNIQUE function is used to extract unique values from a range of data. UNIQUE is only available in Excel 365, and was introduced in 2020. When the workbook is opened in an older version of Excel, the __xlfn prefix appears. Note that the original result is still displayed. However, the formula will not update to show a new result if data changes.

Solution or workaround

If you open the same workbook in a version of Excel that contains the missing function(s), the _xlfn prefix will be disappear and the function will calculate normally. If this is not possible, you might be able to use a another formula that does not not rely on the newer function. Author

Dave Bruns

Hi - I’m Dave Bruns, and I run Exceljet with my wife, Lisa. Our goal is to help you work faster in Excel. We create short videos, and clear examples of formulas, functions, pivot tables, conditional formatting, and charts.