Bonus stocks classification for the purpose of capital gain tax calculation

COA....... Nil 

DOA...... Date of allotment......

For the purpose of calculating Capital gain, the original shares and the bonus shares details are to be dealt separately, i.e., Capital Gain is to be calculated separately.

For the Bonus part, the Cost of Acquisition shall be held NIL and the period of holding shall be from the date of its acquisition / allotment. 

so we end up in paying more tax in case of bonus shares, since market price of shares is being adjusted as per ratio of bonus shares

like take an example of Godrej consumer shares the market price before bonus shares was around 1400 , post bonus shares declaration the cost was reduced directly by around 33-35% , now price is 864

if CoA is taken as zero, the profit w.r.t. current market price will be 100% for bonus shares and hence more tax.....STCG with tax @ 15%

if we sell all principal and bonus shares now, we will end up in paying 40% more tax as compared to if we assume bonus shares same as principal shares with market capital kept constant as soon as share count increased......so whats the benefit of bonus shares???, share holder will end up in loss only

Also in case of official split or demerger the same situation arises as one lot of shares will be new with current DoA and we have to consider them at STCG @ 10% tax

isn't it gap in tax laws for such scenarios???

Yes, Issuance of Bonus Share is not beneficial for the existing shareholders at all, and sometimes not beneficial for the company too. It is beneficial only for the prospective investors. 

It's a tool to the company to capitalise its profits and increase its capital base which has two consequences. The positive consequence is that by increasing the capital base the company looks bigger than in reality it is, which attracts the investors and as the number of outstanding shares increased, the share prices get reduced which again attracts the investors. The negative consequence is  due to increase in the number of shares, in future the Dividend per Share would get reduced, which may demotivate the investors.