Enabling AWS-Generated Cost Allocation Tags, generates a cost allocation tag containing resource creator information. This is automatically applied to resources that are created, and allows you to view and allocate costs based on who created a resource.
Log in to your Master account as an IAM user with the required permissions, and go to the Billing console:
Select Cost Allocation Tags from the left menu:
Click on Activate to enable the tags:
You will see that it is activated: