I am receiving the following error when I create the following formula field on activities:

The value of a parameter contains a character that is not allowed or the value exceeds the maximum allowed length. Remove the character from the parameter value or reduce the value length and resubmit.

Here is the formula - Is this because I am using WHOID?

 Demo_Set__c = true ,
  • 2
    What type did you declare this formula as producing? (I.e. the formula field)
    – Phil W
    Commented Mar 16, 2020 at 22:44
  • @PhilW it is a text field Commented Mar 16, 2020 at 23:37

1 Answer 1


Use NULL instead of "".

IF(Demo_Set__c, CASESAFEID(WhoId), NULL)

Passing in an empty string for an ID value isn't allowed, so that may be the source of your problem.

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