What is a Bonus issue?
A bonus issue is an offer of free additional shares to existing shareholders. A company may decide to distribute additional shares as an alternative to dividend payout. For example, a company may give one bonus share for every 2 shares held.
You will be eligible for bonus shares If you’ve purchased the stocks before the ex-date. If you've purchased the shares on or after the ex-date, you will not be eligible for the dividend. Refer to this article for more info on eligibility.
Refer to this article on Varsity for a detailed explanation on Bonus.