Index: The object of filing is to preserve letters and documents in such a manner that they can be found out quickly, whenever they are required for future references. This object of filing can only be made possible. if letters are filed serially according to some particular method. Therefore, a technique is required which can indicate the exact location of a particular letter which is required for the reference and filed in a file. This particular technique is called index. 

Importance of Index: 

1. In the absence of an index, it would not be possible to find out the name of the customers who have not placed any order since long. 

2. The employees cannot be held responsible for any delay and inefficiency. It will take a lot of time in  finding out the references which will result in delays.