If cell is not blank

In this example, column D records the date a task was completed. Therefore, if the column contains a date (i.e. is  not blank), we can assume the task is complete.

The formula in cell E5 uses the IF function to check if D5 is "not empty". If so, the result is "Done". If D5 is empty, IF returns an empty string ("") which displays nothing"

=IF(D5<>"","Done","")

The <> symbol is a logical operator that means "not equal to", so the expression <>"" means "not nothing" or "not empty". When column D contains a value, the result is TRUE and IF returns "Done". When column D is empty, the result is FALSE and IF returns an empty string ("").

Two results

To display both "Done" and "Not done", you can adjust the formula like this:

=IF(D5<>"","Done","Not done")

With ISBLANK

An alternative is to use the ISBLANK function to test for blank cells. The ISBLANK function returns TRUE when a cell is empty and FALSE if not. To use ISBLANK, you can rewrite the formula like this:

=IF(ISBLANK(D5),"","Done")

Notice the TRUE and FALSE results have been swapped. The logic now is if cell D5 is blank.

To keep the original sequence and logic, you can add the NOT function like this:

=IF(NOT(ISBLANK(D5)),"Done","")