It's recommended to create a process to view and prune contacts in which you no longer have a lawful basis to process a contact's data. This can be done by creating a saved search on your homepage dashboard for contacts that do not have a GDPR tag applied to them.
Go to CRM > Contacts
Click New Search
Choose Doesn't have ANY of these Tags next to the Tags label
Enter all of your GDPR tags
Enter the name of saved search.Select any other users that need access to this list, check the box to Add this search to the User Home and click Save
Example: "No Lawful Basis" or "Non-GDRP Compliant"
Now, go back to your dashboard to see your new saved search. You can click Settings to further customize the report.