Local government authorities levy annual taxes, which are called council rates or shire rates. The basis on which these charges can be calculated varies from state to state, but is usually based in some way on the value of property. Even within states, individual local government authorities can often choose the specific basis of rates - for example, it may be on the rental value of property (as in Western Australia) or on the unimproved land value (as in New South Wales). These rateable valuations are usually determined by a statutory authority, and are subject to periodic revision.[1][2][3]