Lookup columns include workflow status columns, traditional lookup columns to other lists, and person/group columns. This includes the two default people fields “Created by” and “Modified by”. If your list has more than 12 of these, you may receive the following error:
“This view cannot be displayed because the number of lookup and workflow status columns it contains exceeds the threshold (12) enforced by the administrator.”
In SharePoint Online, you’re not able to increase the lookup column limit. Lists created prior to the June 2013 CU update are capped at 8 lookup columns, while those afterward are allowed 12.
However, on-premise SharePoint (server) allows you to change this limit to your heart’s content.