Your just doing something wrong.

Rob & Tammy don’t think I 'm crazy… https://community.skuid.com/t/group-aggregate-model-on-a-formula-field

Just having a little fun. It’s not possible.

The workaround works… seems a little convoluted, but only took 10 minutes to set up and works well. (For anyone reading this post with this issue). Night, Pat!

Caveat to that is when a formula field uses a value stores on a related record and it changes. If everything is derived from the one record then you’re good to go.

Salesforce itself doesn’t allow grouping by formula fields in aggregate queries. A very annoying limitation.

The link posted by Skuidward no longer functions, is there some easy workaround that allows aggregate querying of formula fields?

My strategy has just been to create a plain text field on the object that is updated via a trigger whenever the record is inserted/updated to essentially mirror the formula field (only works if the data referenced in the formula field is self contained / not based off of other objects or changing dates which require more work to get right)