London Local Authorities Act 1996

2At the end of each financial year any deficit in the account shall be made good out of the general rate fund, and (subject to paragraph 3 below) any surplus shall be applied for all or any of the purposes specified in paragraph 6 below and, in so far as it is not so applied, shall be appropriated to the carrying out of some specific project falling within those purposes and carried forward until applied to carrying it out.