I do not see Task/Activity/Event as an option for a Lookup on my custom Lookup on the Case object. I know Tasks are treated differently than other object but I cannot find any documentation stating that it is impossible. Can someone confirm that is it not possible or let me know how to do it?

1 Answer 1


The Task object has a WhatId field (label "Related To") that can be set to the ID of any type of object. This allows zero to many Tasks to be associated with an object, with those Tasks presented as a related list in the object detail page. This is the normal way to relate a Task to some other object: a field on an object that is a lookup to a Task is not supported.

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    You still can't relate a task to a task, though, which I find to be a pretty significant limitation. Imagine you're writing a project module and you want to use built-in tasks. Those tasks can't be linked to each other so you can logically see which tasks preceded other tasks. On the flip side, I recognize that it's rarely useful, and you can work around it with custom objects, but it would be nice to link tasks together.
    – sfdcfox
    Jun 13, 2015 at 16:34
  • Thanks for the reply. Unfortunately, I am using that Task Related To to point to another item and I need multiple Cases to point to a single Task. So, a Lookup would be necessary on the Case object. Jun 13, 2015 at 18:58

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