Dependent Lookup in MS CRM 2016 and D365 Requirement : When a value selected in a lookup, related records for that lookup should be filtered in another lookup. Eg: let’s say, we have Out Of SLA Reason and Out Of SLA Sub Reason lookup (entities). When a value is selected from Out Of SLA Reason Lookup, only related records of that value should be visible in Out Of SLA Sub Reason lookup. Implementation : Create two custom Entities – Out Of SLA Reason and Out Of SLA Sub Reason Create a 1: N relationship (Referential) in Out Of SLA Reason with Out Of SLA Sub Reason. Which creates a lookup of Out Of SLA Reason in Out Of SLA Sub Reason entity. Now go to Out Of SLA Sub Reason form and Out Of SLA Reason lookup on the form. Now populate the data in Out Of SLA Reason and Out Of SLA Sub Reason . Once data populated, go to Out Of SLA Sub Reason and select the related SLA Reason records from lookup for Out Of SLA Sub Reason records . Now go to SLA Reason, SLA Sub Reason entities and create 1: