Any stamp that is cancelled by postal authorities before it is sold is described as "precancelled": the precancellation mark is an overprint. This is usually only done when stamps are sold in large bulk quantities to businesses or other large organizations: the postal service will save the labor of cancelling each individual stamp by precancelling the entire purchased quantity. The overprints also help prevent theft or misuse because they usually include the name of the city or region in which they are to be used. Unlike standard cancellation marks, they usually do not give a specific date, affording the bulk purchaser time to use them at their discretion. In some situations, however, months or years may be included in the overprint to indicate an expiration.