LTCG on equity of demergered shares

LTCG ARISES ONLY WHEN SHARES ARE SOLD. 

Not necessarily. LTCG and LTCL may arise on unlisted and delisted stocks without the sell transaction.

Many companies automatically cancel the shares and delete them from your demat account without your knowledge or without your consent.

https://www.ndtv.com/business/essar-steel-announces-cancellation-of-shareholder-holdings-2157834#:~:text=In%20an%20e%2Dmail%20statement,India%20Company%20Secretary%20Pankaj%20S.&text=Consequently%2C%20the%20entire%20existing%20issued,2019%2C%20the%20company%20secretary%20said.

Such transactions can also cause LTCL 

That is equal to maturity right, that is why taxes are applicable

it is also settlement, When the investment  does not produce any further benefits, it’s called disposal or settlement and taxes applicable on them

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