What is a Book Closure/Record Date?

The ownership of shares of companies traded on the stock exchange is freely transferable by registration. However, shares are many times held by buyers without sending it for registration to the company. In order to be entitled to the benefits such as dividend, bonus, rights etc. announced by the company , a buyer would need to send it for registration. The company announces cut off dates from time to time. The list of members on the companies registers as of these cut off dates be the people entitled to the corporate benefits.