When a listed company announces bonus or even on rumour of bonus , it price on the bourses goes up substantially . Similarly many times , a company demrges one of its arm into another company . The news of demerger of one arm of the company may also trigger the price of shares upwards if investors perceive such a move by the company as a move to unlock the values of shares of such company. For example recently Syntex Industries Ltd demerged its plastic prefab division in another company Sintex Plastics Technology Ltd (SPTL) has been demerged on 12th May 2017 and now listed on stock exchange. In the eyes of many analysts, such a move to demerge plastic division was considered old positive by many stock analysts and market responded the news of demerger proposal with higher prices of shares of Syntex Industries Ltd . In such circumstances , i.e bonus announcements or demerger news- that triggers for rise in stock price, if you do not take proper decision with respect to your holdings , you are going to lose an opportunity to rake in higher gain.