An IPS TAG is a unique identifier given to each Tag-Holder with Nominet (the registry for all UK domain names). Tag-Holders are the Domain Name Companies that provide domain name registration services. They include specialist domain name companies, web hosting companies, ISP’s and others such as web designers. The tag is used to identify the company responsible for the management of a .uk domain. It is a single alpha-numeric sequence, in uppercase, sometimes hyphenated.
If you want a different company to “look after your domain names” you can do this by changing your IPS Tag. For changing the IPS Tag you need to contact the company where you have registered the domain name and ask them to change the TAG to the TAG of your new provider. Some companies will charge a small fee for this change and are reluctant to “let you go” and want reasons for the change. The company you change your domain name to will provide you with their IPS TAG which you need to hand over to the current company, so that they can make the change. The new company might charge a small fee too for transferring a domain name to their business.