You received a subject access request (SAR) from Tapmydata because an individual wants to find out what personal data you hold on them, why you hold it and who you disclose it to.
What is the right of access, or subject access request?
The right of access, commonly referred to as subject access, gives individuals the right to obtain a copy of their personal data as well as other supplementary information. It helps individuals to understand how and why you are using their data, and check you are doing it lawfully.
Where can I find out more?
You can read more about subject access requests on the Information Commissioners Office (ICO's) website. The ICO have also published a comprehensive subject access request code of practice where they explain in detail the rights of individuals to access their personal data.