Here is the use of Use Hierarchy in Dynamics 365 CRM Roll-up Field’s Use Hierarchy option when defining the logic of the Roll-up fields.

Scenario

Let’s consider this out-of-the-box scenario where an Opportunity Rolls up Est. Revenue to the Account it is tagged to. Also, that Account also has another Account set in the Parent Account field.

So, the hierarchy here is Account (Parent Account) -> Account (child Account) -> Opportunity

Now, our demonstration of Use Hierarchy will show where does the Open Revenue (field on the Account) should Roll up from it’s own Account or from the Opportunity of the child Account’s Opportunity as well.
You’ll see a Hierarchy Icon to all records that participate –


And when you select either of them, you’ll be able to click on View Hierarchy button on the view’s Ribbon


This will show you how the Accounts are arranged in hierarchy


And here’s where you can access your Hierarchy Settings

Let’s see!

Use Hierarchy in Roll Up fields

Here’s how you would see the option to switch between Use Hierarchy in the Roll Up fields in Dynamics 365 –

Use Hierarchy: YES

Now, assuming this is set to Yes and it selects the OOB relationship that defined this hierarchy

1. Consider the child Account “Alpine Contoso” (This is a child account of “Alpine Ski House Main“)
   
   
   
2. And this Account Alpine Contoso has it’s own Opportunity worth of $25K
   
   
   
3. Now, let’s look at the Alpine Ski House Main‘s Opportunity which is worth $30K
   
   
4. Now, the Open Revenue for this child Account “Alpine Contoso” is $25
   
   
5. However, since we are using Hierarchy as YES and selected the relationship between the self-lookup of Account itself, this value will also add up to the Open Revenue of the parent Account “Alpine Ski House Main” is $30K + $25K = $55K
   
   
   Here, we saw that the Open Revenue from the child Account too Rolled up to the Parent Account.
   

Use Hierarchy: NO

Assuming, the Roll-up field is now set to NO to Use Hierarchy, let’s see the difference on the Parent Account “Alpine Ski House Main” itself.

1. If we look at the Alpine Ski House Main‘s Open Revenue value, it’ll only have $30K
   
   
   
2. This $30K belongs to it’s own child Opportunity and not child Account i.e. Alpine Contoso‘s Opportunity.
   

Hope this was helpful! Here are some more D365 posts which you might be interested in –

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Thank you!!