Financial statements of one accounting period must be comparable to another in order for the users to derive meaningful conclusions about the trends in an entity's financial performance and position over time. Comparability of financial statements over different accounting periods can be ensured by the application of similar accountancy policies over a period of time.
A change in the accounting policies of an entity may be required in order to improve the reliability and relevance of financial statements. A change in the accounting policy may also be imposed by changes in accountancy standards. In these circumstances, the nature and circumstances leading to the change must be disclosed in the financial statements.
Financial statements of one entity must also be consistent with other entities within the same line of business. This should aid users in analyzing the performance and position of one company relative to the industry standards. It is therefore necessary for entities to adopt accounting policies that best reflect the existing industry practice.
If a company that retails leather jackets valued its inventory on the basis of FIFO method in the past, it must continue to do so in the future to preserve consistency in the reported inventory balance. A switch from FIFO to LIFO basis of inventory valuation may cause a shift in the value of inventory between the accounting periods largely due to seasonal fluctuations in price.