What is book closure date?
The time period when a company will not handle adjustments to the register, or requests to transfer shares.
The book closure date is often used to identify the cut-off date determining which investors of record will be sent a given dividend payment/bonus issue/split stock etc.
The stock of publicly-traded companies changes hands daily as investors buy and sell shares. Due to this, when a company declares it will pay a dividend or issue bonus or split stock, it must set a specific date when the company will "close" its shareholder record book and commit to sending the dividend to all investors holding shares as of that date.