I wonder if you have to have planning permission for change of use... in which case, the council will charge you for your planning application fee - here's the site that tells you all about it - http://www.planningportal.gov.uk/
Are you saying that you have lived on the land yet never had PP for whatever you live in? If so, then it is likely you are being asked to pay the std Planning Application fee for a Certificate of Lawful Development for the site. And if so, then that is correct that they will charge you for it.