Formulas that return dates and times as negative values can also show as #. Microsoft Excel might show # in cells when a column isn’t wide enough to show all of the cell contents. Excel for Microsoft 365 Excel for Microsoft 365 for Mac Excel 2021 Excel 2021 for Mac Excel 2019 Excel 2019 for Mac Excel 2016 Excel 2016 for Mac Excel 2013 Excel 2010 Excel 2007 Excel for Mac 2011 More.