Alt + N C B inserts an in-cell checkbox (Insert > Checkbox). It does not work on Mac because Excel for Mac has no Alt key ribbon shortcuts. Install Accelerator Keys, then press Option, N, C, B. You also need Excel for Microsoft 365, because older versions do not have in-cell checkboxes.
Command: Insert Checkbox
This is how to do Alt + N C B on Mac in Excel with Accelerator Keys, the native ribbon and alt key shortcut solution for Mac users who get more done with Excel.
Alt + N C B inserts a checkbox into each selected cell. Checkboxes toggle between checked (TRUE) and unchecked (FALSE). They are useful for to-do lists, tracking completion status, and interactive dashboards.
There are two common causes. On a Mac, Excel has no Alt key ribbon shortcuts, so the keys do nothing. Accelerator Keys adds them. On any computer, in-cell checkboxes are a Microsoft 365 feature, so Excel 2021, 2019, and 2016 do not have Insert > Checkbox.
In Excel for Microsoft 365 on Mac, select the cells and click Insert > Checkbox. With Accelerator Keys, press Option, then N, C, B.