Handle Null in IF Statement

Hi Rich_Wyeth 

Use the below M Code:

= Table.AddColumn(#"Due Days", "Due Category", each 
    if [Due Days] = null then null 
    else if [Due Days] >= 0 then "Overdue" 
    else if [Due Days] <= -365 then "Over 12 Months" 
    else if [Due Days] < -180 then "6-12 Months" 
    else if [Due Days] < -90 then "3-6 Months" 
    else if [Due Days] < -30 then "1-3 Months" 
    else "1 Month"
)

hi Rich_Wyeth ,

try like:

= Table.AddColumn(

    #"Due Days", 

    "Due Category", 

   each 

    if [Due Days] >= 0 then "Overdue" 

    else if [Due Days] <= -365 then "Over 12 Months" 

    else if [Due Days] < -180 then "6-12 Months" 

    else if [Due Days] < -90 then "3-6 Months" 

    else if [Due Days] < -30 then "1-3 Months" 

    else if [Due Days] =null then null

    else "1 Month"

)