ShaneDevenshire wrote...
Here's one way:

Change your formula from

=IF($M20,$M2,IF($M2=0,"NA"))

to

=IF($M20,$M2,IF($M2=0,1))

Create the following custom format and apply it to the whole column:

[=1]"N/A";m/d/yyyy
....

Why not leave the column A formulas as-is and sort on column M?

Or make the column A formulas simple, e.g., A2: =M2 and format using

[=0]"NA";mm/dd/yyyy

? If these records sort correctly with missing column M values as 1 in
column A, they'd also sort correctly with missing column M values as 0
in column A.