Financial Statements are drawn to provide information about growth or decline of business activities over a period of time or comparison of the results, i.e. intra-firm (comparison within the same organization) or interfirm comparisons (comparison between different firms). Comparisons can be performed only when the accounting policies are uniform and consistent.
According to the Consistency Principle, accounting practices once selected should be continued over a period of time (i.e. years after years) and should not be changed very frequently. These help in a better understanding of the financial statements and thus make comparisons easy.
Although consistency does not prevent change in the accounting policies, but if change in the policies is essential for better presentation and better understanding of the financial results, then the firm must undertake change in its accounting policies and must fully disclose all the relevant information, reasons and effects of those changes in the financial statements.
