Is it compulsory to tender shares in a buyback if I have shares in my demat account?

Buybacks are optional. It's shareholder wish to tender or not. It's not compulsory to tender shares in a buyback offer.

In some cases shareholders do not tender the shares in buyback:

1. When the share price reached close to the buyback price. For example:
   • Xyz company is trading at Rs 75 per share 
   • The company come up with a buyback offer ar Rs 85 per share
   • The share price reaches around Rs 85 close to the buyback issue closing date. 
2. The buyback size and acceptance ratio are too small.
3. Shareholders invested for the long term.
4. Complicated paperwork for non-individual accounts.
5. The share prices usually go high after buyback offer.