Filter Custom Child Record

I have created a custom record to hold a list of text names on a customer record. This record type will be used to differentiate areas/divisions of a customer based on their definitions, so it is strictly just a list of names. There are two fields Company and Tag Name. Company has been set as record is parent and the new type is showing up fine on customers as it should.

My problem is that even though a new tag is set with a company the billing tags show up on all customers. I need to have them only show up on customer that is listed in the customer field. I am assuming  it is a filter problem, but I can't find where I have gone wrong. I have set the Company field with record is parent and filtered the Tag Name field on Company for source list and tried both Company and External ID for the source from. The list of 5 test tags still show up on customer records