The period during which a firm will not process changes to its books or requests to transfer shares.

The book closure date is frequently used to determine the cut-off date for determining which record investors will get a dividend payment/bonus issue/split stock, and so on.

Investors buy and sell shares of publicly traded firms on a daily basis, resulting in daily stock turnover. As a result, when a corporation declares that it will pay a dividend, give a bonus, or split stock, it must specify a particular date on which it will "close" its shareholder record book and commit to distributing the dividend to all shareholders who own shares as of that date.