Could someone please tell me if I need to declare where I have used a Wordpress theme that I bought?
I was just thinking someone could visit the website I have created and as far as I know there is no way of knowing if the theme used as a legit licence.
There is a degree of trust involved. You do not need to officially register it or anything.
There are some authors who give buyers the option of things like auto-updates etc. which will mean that the installation can be tracked but it’s down to the buyer and not a way of being intrusive