Regulation 107 of the Representation of the People Regulations 2001 places restrictions on use of the electoral register by the local authority. In summary no councillor or employee of the council may
supply a copy of the full register to any person other than to another councillor of or employee of the same local authority;
disclose any information contained in it that is not included in the edited register; or
make use of any such information.
It is a matter for local authorities to decide whether to share council tax data between departments within their organisation.