In the House of Commons the Register of Members' Interests allows MPs to declare any interests that they hold outside Parliament. Interests include outside jobs or consultancy work, gifts or membership of organisations that might affect their position in Parliament. In the House of Lords the Register of Lords' Interests is where Members of the House of Lords declare the following kinds of outside interests: i) Consultancy work which involves payment; ii) Financial interests in businesses that are involved in lobbying Parliament; iii) Any other interests which may affect the public's opinion of the way in which the Lords carries out its duties (this is optional). Three other Registers exists and they are as follows: Register of Interests of Members' Secretaries and Research Assistants; Register of All-Party Groups; Register of Journalists' Interests
Further information on this subject can be found from the following links.
Register of Members' Interests
Register of Lords' interests