The Local Government Finance Act 1988 gives broad authorisation for regulations to be made about alterations, which can include alterations by the Valuation Office Agency to maintain the list accurately, or proposals by interested parties to change the list. The regulations have differed widely, changing the time-frame of when alterations are effective. For example, proposals to alter the 2000 rating list by an occupier were restricted to take effect in the financial year in which they were made, but the 2005 rating list removed this restriction, so that a successful proposal can have effect as far back as 1 April 2005.