A method is described of providing validation data associated with a subscriber line of a telecommunication network. The method includes obtaining line data of the subscriber line wherein the line data is suitable for interrogating a line identification database (LIDB). The method interrogates the LIDB with the line data to obtain reference subscriber data associated with the line data, and processes the reference subscriber data to obtain validation data associated with the subscriber line. The invention extends to a subscriber line validation system to validate a subscriber line of a communication network.