I want to explain how to use replacement key functionality on AX 2012. D365FO has the same ability too. Replacement key helps you to link your parent child tables through the parent table RecId value but on the user interface it will display the string data that makes more sense to the user. With this ability you don't have to struggle with preparing unique string field to link parent and child table which we all know it could be a nightmare. Let's start with how can we activate replacement key functionality on AX 2012 First create the parent table Table name is ParentTable and it has two fields Id and Name. Id field is the unique field. After creating the index change the Allow Duplicates property to No and change the Alternate Key to yes. On table properties you should be able to find your index name under ReplacementKey. There can be only one replacement key per table. Parent table is ready now create the Child table with one field ChildName When you create a relation on