M Query Returns Error for Calculated column referencing null values of date column

Use this:

try if([Actual Closed Date] >= #"Parameter Date Closed Start Date" or [Date Received] >= #"Parameter Date Received Start Date" and [Deal Status Display] = "Open") then "True" else "False" otherwise null

see also: 

Error handling - Power Query | Microsoft Learn

This gives Token eof Expected error.

You need a "try" in front of the "if". 

The syntax is: 

try [THIS] otherwise [THAT]

where [THIS] is what you want to calculate i.e. your entire "IF" statement, and [THAT] is what you want to display if your calculation fails for any reason. 

This is the code:

try if [Actual Date Closed] >= #"Parameter Date Closed Start Date" or [Date Received] >= #"Parameter Date Received Start Date" and [Deal Status Display] = "Open" then "True" else "False" otherwise null

It was Actual Date Closed, not Actual Closed Date, and there were some erroneous brackets

If I type in the code exactly as described in my previous post, including the "try" at the beginning, and without the erroneous brackets, it works: 

Please mark the solution as "Accepted" if this works for you.  Thanks.